ladishd: do a better cleanup on project unload and on load failure. Partial fix for #117
The project state now is can now have more than one state. The project
unload sequence now first removes all connections, then stopps all
apps, and as last step - clears the graph. When project load fails,
ladish_room_unload_project() is not called anymore, because unloading
of room even without apps is now a multistep process. Instead, a new
function, ladish_room_clear_project(), is introduced. It is called
when project load fails and as last step in project unload.