Overlay support for legacy camera libs

1. Rename OverlayHtc to Overlay in file names
2. Use BOARD_USES_LEGACY_OVERLAY to enable

Change-Id: I8c5cb03fa73f1442191404c80fb376f65461923d

Conflicts:
	libs/ui/Android.mk
Revert "Overlay support for legacy camera libs"

This reverts commit a14126bb668a672d27178705ee0e3b0c024eb3d1.