After performing a search, there's already a clear search link in
the view. Without a border around the search bar, the clear icon
looks a little lonely and strange all the way over on the right.
I offer that users have plenty of ways to clear text boxes and
we needn't give them this one.

Requires some small tweaks around various places we have icons in
use. In fact, this actually eliminates a lot of the small tweaks
in favor of more flexible alignment.

Rather than absolute positions and padding and whatnot just set
the width on the input element and set white-space: nowrap to ensure
it and the icon are side-by-side.

Better to use data attributes for signaling the intent than to
be overloading the CSS class.

Clean up and delete a few unneeded things.

Make the bridge service a factory instead

 - Remove unused support for options
 - Simplify the handling of scope
 - Make it a simpleton, and register the class as the constructor function.

Also updated all tests.

Kudos to @tilgovi for the feedback and ideas.

Fix sidebar's focusing on annotation cards

When the user moves the mouse over a highlight in the document,
the corresponding annotation card (in the sidebar) is supposed
to be highlighted, to indicate focus.

Our mechanism for this was broken in 3 different ways:

1. AnnotationUI service's focusAnnotations() method was working
   with annotation IDs. However, annotations being created
   right now don't yet have ID, only tags. So we should be working
   with tags instead. (Like we are, in many other cases
   when cross-frame communication communication is done
   around annotations.)

   I fixed that, and also updated the corresponding tests.

2. In controllers.coffee, when we were trying to check if a given
   annotation has focus, we were using the tag value, while on
   the other hand, it was not the tag, but the id that was put
   into the map. Of course this didn't work.

   Since now we are consistently using the tag, no change
   was needed here.

3. We are putting $$tag:true pairs into the map, but when
   checking for membership, the `in` operator was used.
   That works for lists, but not for maps. For maps, we simply
   have to read out the value belonging to the given key,
   and see if it's true.

After fixing these problems, the feature works again.

Replace type() typechecks with isinstance()

I will let it have its way.

That shaves ~50kB off the minified bundle.

Close #2019

Fix #2013