Fix commit message for the previous commit

Implement consistent Squeezer item actions

- Implement actions as per:
  https://docs.google.com/spreadsheet/ccc?key=0AoZbzjFHlorsdE1MY2FFeE1jYjRkTEw1aV9qUURuV3c&usp=sharing
- Configurable actions are moved from activity to view logic, to make it work
  from all lists, i.e. album list and search result for albums, and song list,
  search result and playlist songs for songs.
- Call default and context menu actions through the adapter, to enable reuse
  for search results.
- Add PlayableItemAction.Type.NONE and use this as the default for songs.
- Add an ActionBar/options menu entry to play/queue all songs of activities
  showing songs
Fix items not loading after resume from sub-activity

Responses which come in after callbacks have been unregistered are discarded,
but they are marked as ordered, so they are are not reordered when a view is
requested.
We cancel outstanding orders after unregistering callbacks to solve this.
Correctly unregister songlist callback

This fixes a potential activity leak, cause the service keeps a reference to
the callback, which holds a reference to the activity.
Enable Android Studio and the Gradle build system

Ignore workspace files and add gradle build files.
The project can be imported into Android Studio using gradle.build.
Cleanup and polish SqueezerBaseListActivity

- SqueezerBaseListActvity: Initialize image fetcher on demand, so it can be
  used before onCreate is called.
- Do not leak pages when items are reordered, and prevent previous items from
  showing briefly.
Update the UI on return from browsing songs of a playlist

Use startActivity for result to start the child activity, and update the list
with any changes, in onActivityResult in the parent activity
Merge branch 'actionbar' of github.com:kaaholst/android-squeezer into actionbar
Merge remote-tracking branch 'kaaholst/actionbar' into actionbar

* kaaholst/actionbar:
  Update the UI on return from browsing songs of a playlist
  Cleanup and polish SqueezerBaseListActivity
  Enable Android Studio and the Gradle build system
  Correctly unregister songlist callback
  Fix items not loading after resume from sub-activity
  Fix commit message for the previous commit
Use Gradle versions of 0.5.1 and above, per
http://tools.android.com/knownissues.