Revert "Remove dock home support."

This reverts commit 7c135205f2f4c192299ad0215276e9e481bccaa5.

Conflicts:
	policy/src/com/android/internal/policy/impl/PhoneWindowManager.java

Change-Id: I7f8cae0f29d996c4729c4ca1c929f7e9b9a0df0c