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>
Merge branch 'cm-10.2' of github.com:CyanogenMod/android_packages_apps_Gallery2 into cm-10.2