Fix FAB state and transitions.

+ Change to dialpad FAB in search (used to stay as add contact
FAB, if we were in the Contacts list).
+ Position dialpad to align end in search (used to stay in the
center, if we opened the search from Speed Dial).
+ Restore correct position/icon when exiting search.
+ Add correct FAB scale in/out behaviors in for transitions
between lists fragment and search UI, search UI and dialpad,
in particular for when the FAB changes position from END to
MIDDLE when going from search UI back to Speed Dial.
+ Add FAB scale in/outs for showing/hiding the soft keyboard.

Bug: 21161760
Change-Id: Idbddbac161e459e3708d43395850d80927d5e448