Add Slim recent app screen, (1/3):

Thanks to SlimRoms and Gabrielle Mariotti:
https://github.com/SlimRoms/frameworks_base/commit/760413134a5efe60c1d4473322e467152d71c80b
https://github.com/SlimRoms/frameworks_base/commit/9c1c3c0955d51adc589ec6fbb667a0ae482de24e

Additional changes to the original commit:
- Use Holo Dark Theme