[1/2] base: add switch to last app as navigation ring target

Was actually based on https://github.com/omnirom/android_frameworks_base/commit/2a7f6e1f19b06cdfe647e87eee8eb11860b09a2e

PS2
much easier :)

PS3
whitespaces

Change-Id: I31f11fcd0efb90f007017fa16567e6711002ecc8