Apollo: Use correct preference keys for artwork download

* These settings were not being respected because the preference key was
  wrong.

Change-Id: I2f6733b6de206a76ce1f6899beced36922653b05
Apollo: Avoid crash when attempting to load many items

* Thread pool executor will reject additional tasks when it has
  exhausted it's queue space causing Apollo to crash.
* Load default artwork if executor is too busy.

Change-Id: Ie25182ede0cfbd0ca8595dbb1f8c024a13a09d93
Apollo SleepMode

Change-Id: I074b10a26daf116da4d6d21d6d26724f4c5b04cc
Apollo: Catch NullPointerExceptions

Sometimes it fails to get image and throw npe. (especially when connected with weak wifi, etc)

Change-Id: I23c0e74783f43bfc067c66d694070e9f907f0d8c
Make this a bit more consistent with the KitKat UI theme

Patch Set 1 - Here are some images to show what it looks like
http://i.imgur.com/FALx2z6.png
http://i.imgur.com/mCD4Jq0.png

Patch Set 2 - Got the remaining of the Holo Blue Light drawables to match
Before http://i.imgur.com/SxPe53D.jpg / After http://i.imgur.com/k8FMxiR.jpg

Change-Id: I24679e2219061b5e5e79d1cd467fbe944057f153