Trebuchet : Default workspace improvements

This reverts commit b54b34edd5c87e6d0702793b423b14dc24fb1076

Fix bug for mdpi devices crash loop.

Revert requires overlays to know if GSF installed,
adding a run time check to load default workspaces.

Add in additional overlays per density for new LauncherModel
and LauncherProvider 4.4.3 logic.

Change-Id: I5709182521e80d273e892eb3310abd68acac95ad