Add connector handling functions. Start tracking is_implicity in
the connector state.  Eventually, this field should be tracked
exclusively in a connector state.

Now that plane and connector states have been created, we can also
activate the code that use CRTC state.
Signed-off-by: Sinclair Yeh <syeh@vmware.com>
Reviewed-by: Thomas Hellstrom <thellstrom@vmware.com>