Add custom views and third party views to the palette

Add custom views and third party views to the palette

This changeset adds a new category to the palette, "Custom & Third
Party Views", which is populated with android.view.View subclasses
found in the current project (or any of its libraries), and in any
jars included by the project. They can be dragged directly to the
canvas, and control clicking on the palette entries will jump to the
source.

There are a bunch of adjustments in various places to make working
with custom views better - from ensuring that we don't use fully
qualified class names in default ids, to showing the Java class icon
for custom views in outline and elsewhere, to making zero-sized view
highlight and expand when selected like we do for laoyuts - since with
custom views it's quite easy to end up with an "invisible" view that
you can't see after dropping it.

There are also some fixes to the code which looks up third party and
custom views (which was already used by the Wrap In refactoring) - to
handle inner classes, to filter out non public or abstract classes,
and most importantly to only include views reachable from the current
project (since the view search necessarily is workspace wide.)

Change-Id: If1d8c7e5c7dd907a68d8d0962e85c5144e911503