This is a workaround, until we can get the forced
log-in workflow properly working for these cases.

Closes #364.

Support for annotating multiple frames

Closes #779

This code was moved from the host to the guest but I forgot to remove
it from the host.

Regression.

Closes #749
Closes #752

Several benefits:
- Custom open/close sidebar toggle is now possible for publishers
- The frame div holds the background image now, which means publishers
  can customize the background behind the annotation sidebar

Also, the heatmap is now the drag handle and it's finally possible to
open the sidebar via a drag action.

Closes #685

In always-on mode clicking highlight now opens the sidebar.
Fixes #669

We really need to get off maintenance.

Inject the heatmap into the host frame using the default embed script.

It will be possible after this to make vanilla embed codes available
which can be used for headless operation or inserting the heatmap in
guest frames.

Fundamentally, the heatmap is altered to behave as though it's inside
the same frame as the annotations. That makes it easier to access
the highlights directly, rather than the pre-resolved jquery that
was being serialized across the bridge before.

Since it is now necessary for the reply counts to be known outside the
sidebar, the bridge is changed to support updating annotations and the
sidebar application is changed to bubble updates through ancestors.

Since iframes cannot have visible overflow the z-index constraints
required to have the heatmap still appear attached to the sidebar
dictated that the controlbar move outside as well.

Adds query parameters when embedding to create embed codes that have
no plugins loaded. This is useful for custom embeddings.

Lastly, I took this opportunity to improve the up/down buckets with the
help of the jquery scrollintoview plugin, which should ensure that
this function works even in situations with nested scrollable panes.

Also, closes #464.

The host page annotator is split into a host and guest version. The
`Annotator.Guest` class implements most of the behavior from the
old `Annotator.Host`, but leaves out everything to do with the widget
hosting aspects (opening, closing and coordinating drag resize with
the sidebar frame).

The bridge is improved to support multiple connections and multiplex
RPC calls. Connections are established by probing other frames to
discovered other bridge annotators. A frame may act like a DHCP
server, responding to discovery probes and offering to connect.

The annotator service is refactored to behave more reasonably with
service and dynamic frame discovery. Rather than assuming that
document metadata is fetched from a single frame, entities from
all frames are registered when they connect. The Store plugin is
patched to load only links that have not previously been loaded
so that API calls can be made as additional entities are registered.

Most functionality, aside from highlight mode, is broken. This is a
result of the difficulty of dealing with the heatmap when it may be
hard or impossible to determine the real offsets of the annotated
frames relative to the offset of a global heatmap. The changes to
extract the heatmap were left out of this commit in order to keep
the size of an already large commit down.

Heatmap: introducing gapSize parameter.

Added link to contact page in username menu so that users could more easily submit feedback.

CSS Improvements

Some cleanup of the editor hide/show entanglement with creation events
is very desperately needed.

Closes #761

+Moved time closer to right hand side of annotation card (closer to triangle).
+Used same style as search x for notifications.
+Fixed time position when "show differences" is checked.
+Revised standalone page.
+Made slight improvements to streams CSS.
+Fixed: top bar on streams should stick to top of page and not float

The `updateReplies` event is unhelpful spaghetti when we can more
clearly watch the collection of thread children that's kept up to
date by the threading plugin automatically.

Utilize `annotation.thread` more.

Help page
Fixes #680 

The clustering algorithm uses this gapSize parameter (it was a constant before) to determine if an annotation is far enough or not from the current bucket position to merge the annotation into this bucket.
As a constant it was set to 180, but now it has a default value of 60 to make the clustering less agressive.