Add further CLI commands

[Doralitze]

We also need commands to

• [x] load a show file
• [x] apply the current show file
• [x] go to a scene
• [x] update constant values
• [x] cue control

Furthermore we should change the socket to be a qt one in order to be able to send messages from the external commands and use signals.

[Doralitze]

The cue can be controlled using the filter update command.