Prohibit uninstall of the default (or only) home app

We suppress the ability to uninstall (including uninstall of updates to
system-bundled apps) when the package in question is either the only
installed home app, or has been explicitly tagged by the user as the
"every time" home app among all those installed.

Bug 14162565

Change-Id: I582bb0d2abf0911ac68813f4c7e6fd7d17bfc2ca
Merge remote-tracking branch 'origin/kitkat-mr2-release'