Added core startable

This will make sure that panels of preferred packages are shown by
default if there are no selection of provider and that panels will be bound on
start.

Test: manual, remove provider selected and observe.
Test: atest ControlsStartableTest
Fixes: 266703958
Change-Id: I04b8e442eb6336b4f7095055cb82a88f6f7530bc
7 files changed