Following the plan outlined in #687, restructure the Redux store as
follows:

 - Move the entry point from `services/annotation-ui.js` to `store/index.js`
 - Move the modules which define bundles of reducers, action creators
   and selectors to `store/modules/{module-name}.js`
 - Move related utility code to `store/{module-name}.js`

Move sidebar services to src/sidebar/services/

Following the plan outlined in #687, move services into a `services/`
directory.

The definition of "services" in that plan (a possibly stateful module
that handles interaction with an external party) is slightly more narrow
than what constitutes an Angular service (a stateful singleton that has
dependencies on injectable services/values).

However as a first approximation most Angular services are services as
defined in #687, so I've simply moved them all to the `services/`
directory.

Rename src/sidebar/{store => services/api}

Give the service which provides a client for the Hypothesis API a more
obvious name and place it in a `services/` dir in accordance with the
plan outlined in #687. The previous name of "store" was particularly
confusing because of the existence of another kind of unrelated store
(the Redux one) in the application.

The service was previously registered with the `factory` method but has
the same structure as all the other services which are registered with
`service`, so I changed that for consistency.

Show the world icon only for open groups in the groups dropdown.

ADR: Sidebar application architecture

private group icon otherwise.

Fixes https://github.com/hypothesis/product-backlog/issues/513

Default to notes tab when only notes present

`selectedTab` is set to "note" rather than "page" if only page notes are
present.

This adds two tests that verify the annotations tab is selected
when there are annotations present and the page notes tab is
selected when only page notes are present.

Change the default tab to focus on page notes when there are
no annotations and only page notes in a group. This way it
directs the user where they need to go. Less clicking == yay!
If there are no annotations at all, the annotations tab should
be selected.

Allow multiple state modules to handle the same action

In some cases multiple state modules may need to handle the same action.
For example, when annotations are loaded or unloaded we may want to
update both the set of loaded annotations and also the current
selection.

This commit changes the `createReducer` helper and the code that uses it
in `reducers/index.js` so that multiple state modules can define update
functions that handle the same action.

Note that all update functions get the same, _previous_ state as input
and there is no guarantee on precedence if they return conflicting
updates.

See also: https://redux.js.org/faq/actions#is-there-always-a-one-to-one-mapping-between-reducers-and-actions

Remove activity page links for third-party open groups

Activity pages are currently only supported for open groups belonging to
the h service's first party authority.

The team has agreed that the best way to resolve this would be to only
include the "activity page" link in the `/api/groups` response for
groups where that is supported. However to give us more time to hammer
out the API details, we are committing a small change to the client in
the interim.

Specify npm package version to publish to S3

Sometimes the "Publish" step has ended up publishing version N-1 to the
CDN when building the tag for version N. I believe this happens due to
npm's package publishing API not guaranteeing immediate visiblity of the
latest version when it returns. If the publish task runs before the
update has propagated inside their network, then the publish step
re-uploads the previous version to the CDN.

This commit attempts to resolve the issue by specifying a package
version explicitly. We might find that this is not enough and that the
publish step either has to wait until the update has propagated or we
have to use a locally-built tarball.

Fixes #602

Pass "authority" query param when fetching groups list

Without this argument, the "h" service does not know which authority's
groups should be returned if the user is not logged in.

Show a list of groups for logged out users.

At the moment we only show one group i.e Public for logged out users.
we should also show those groups to logged out users.
See https://github.com/hypothesis/product-backlog/issues/417

Only wait for document URI before fetching groups in sidebar

Fixes a regression after 36c46608 where the stream and single
annotation page views failed to load.

36c46608 made the groups service wait for the host page's document URI
to be determined before making a call to the `/api/groups` endpoint
passing that URI as a parameter. In the stream (`/stream`) and single
annotation page routes, there is no host page and so
the promise returned by `getDocumentUriForGroupSearch` never resolved.
Avoid waiting for this URI in that case and avoid passing the
`document_uri` parameter to the `/api/groups` endpoint.

This commit introduces a new `isSidebar` test rather than using
`annotationUI.isSidebar` because that piece of app state is not yet
initialized at the point when `groups.load()` is called in the route's
`resolve` function in src/sidebar/index.js.