Fixes to support ActionBarSherlock.

AlertDialog.show() and Dialog.show() now temporarily pause the UI thread.
Libraries that don't have an AndroidManifest.xml now default to "org.roboletric.default" for package name.
Centralized ApplicationInfo and PackageInfo creation.
Implemented AssetManager.openXmlResourceParser().
More hacks to get ViewRootImpl into the right state.
RoboWindow.getDecorView() runs with looper paused.
Remove commented-out code.
Fix bug in ShadowHandler.sendMessageAtTime().
Remove ShadowMessage.
Capture calls to System.nanoTime() so things are more deterministic.