Switch from using TabHost to using ActionBar

There is a lot of annoyance involved with this, since all of our tabs
have to be Fragments instead of Activities.

Notably:
 - Click handlers have to be wired up in Java, not XML
   (we could make this easier with something like Android Annotations)
 - When nesting Fragments inside other Fragments, like with the
   SupportMapFragment inside the main map tab, you must create the
   fragment from Java when the fragment's layout is inflated, and
   recreate it each time the fragment is reused.  Because of this, we
   hide our tabs in the background instead of detaching them, to avoid
   losing the map state
 - You can't dynamically change the view using setContentView, like
   the ProfileDisplay activity was doing
 - You have to do cleanup when adding Views to a fragment dynamically,
   because the fragment may get detached and reused.
fixup issue with listdisplay???
Add generated Holo style overrides

Files were generated using http://android-holo-colors.com/ and
http://jgilfelt.github.io/android-actionbarstylegenerator

All of the themes_holo_custom.xml files were then manually edited to make
@style/holo_custom inherit from @style/Theme.Actionbar_custom