Added an api to uninstall a packge with active DAs

The api deactivates all the active admins in the package, then force
stops the package and starts the uninstall intent for the package. This
is intended to provide an easy way for a user to delete a misbehaving
Device Admin

Bug: b/22359208
Change-Id: Ic7ddd89ef6db53e7e76f805808d9e806100374db