Revert "Remove dock home support."

This reverts commit 7c135205f2f4c192299ad0215276e9e481bccaa5.

Conflicts:

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

Change-Id: I54e67a0e36d8e8541dcb8217f3c7fddc5a93a6bf