Simplified alpha listview animation

most of these animations look like garbage.. so lets
just include a simple alpha one without interpolation
because it is not needed.

PS2: some cleanup and fix potential null pointer
PS3: small tweak to speed up alpha animation.. may tweak
transparency levels next..

TO DO: make it dependent on the values set in developer settings

Change-Id: I79c184e9125689fa88d0b2cf160e420517f3a91c
Merge "Simplified alpha listview animation" into jb43