Getting RTL up to a reasonable state in Launcher3

-> Fixing random page jumps from one edge of page view to another (issue 10846070)
-> Fixing screen -1 overlap (issue 10861684)
-> Fixing callbacks / transition state related to Custom Content in RTL (issue 10858355)
-> Overview mode now works in RTL
-> Making visible page range code RTL-LTR independent

Change-Id: I4dcc6127a02bf6669f5a1e8e1b62b340b60a5edc