Bring the baby back: longpress back button to kill the app [2/2]

this old CM baby (made by @rascarlo) is still useful
till kufi does his magic on the navbar :D

Patchset2: use the new L SwitchPref slider instead of the old
checkbox

Change-Id: Id45b1d28b6864e6bcdfc3c26b4d4137f6369fb38
Fix memory leak issue in application settings

If opening Main menu->Settings->Apps, and rotating the phone
about 50 times, Settings force closes and out of memory occur.
This is because after ManageApplications onDestroy, references
of ApplicationsState have not been release. So, they will not
be garbage collected. It leads to OOM and force close. To
avoid this we need to release the references of
ApplicationsState when ManageApplications onDestroy.

Also, when exiting ManageApplications or InstalledApps in
Settings there is a memory leak due to not releasing some
objects. This fix releases the Session objects to avoid
memory leak.

Change-Id: Icca7100bded0653a4ec7f2b4bd48a29262432a3b