Restore Overscrolling

Oooohh... Bouncy!
This reverts commit 9d32d24d
("Remove overscrolling"), fixes some minor issues, updates the
code to the current state of the scrolling and view classes,
updates the conflicting API method IDs, and adds a Setting to
toggle it.

Change-Id: I3f608fbaccd7d578ca21b2679b87916fbc63bf6d