Gallery2: Refactorize Pools class

Move Pools to other package to avoid the conflict name with the
frameworks base one, which has a different implementation.

Change-Id: Idbe79773232a957a1ef230326a142e126eebb8b4
Signed-off-by: Jorge Ruesga <jorge@ruesga.com>
Gallery2:Dark UI changes

Gallery2: TRDS goes Slim

Change-Id: I49f42c1b10e654502d46ddb88ac2343efe747a41