profiles: Make the actions wizard buttons show up

The "back" and "finish" buttons weren't being shown at all in this
layout, which made it impossible to add profiles.

Change-Id: Ib6b52430c25ed7445ca8e3c1249b7fccd21c3c69
profiles: Make the floating action button more material-y

This makes the FAB look consistent with other fabs across the system,
it adds animated elevation, changes the icon color to white but mainly
fixes the size which was completly wrong.

Change-Id: Ib8b2d54869a6a10958c24bcc0fab1224fd07fadd
TrustedCredentials: Don't crash when the activity is paused

If you press Settings -> Security -> Trusted Credentials, then press
 back before the loading finishes, the loader async task will still
try to dereference the activity which will cause an NPE.

This patch fixes that by getting and holding a reference to the
context in the beggining and bailing early if it is null.

Change-Id: Ie03734d5f184821df5d8729fc4a16eb51cdeebf5