Allow MIDI-based scene changes to trigger scene-attached MIDI messages

Currently, we can assign MIDI messages to be sent when a scene is engaged, but these messages are only sent when the scene is engaged via the physical footswitch. If you select a scene via MIDI (for example using CC#43 the MIDI messages attached to it are not sent. I propose that they should be - selecting a scene is selecting a scene. This should also include triggering the appropriate stomps via MIDI when in scene mode.