Move SystemComandMap from ChatScene to its own component.
Create message specific commands with their own parser.
Fix separators not shown correctly in TextInputContextMenu.
Reviewed-on: https://git.kske.dev/zdm/envoy/pulls/74
Reviewed-by: kske <kai@kske.dev>
Reviewed-by: DieGurke <maxi@kske.dev>
Additionally removed ability to decide whether exceptions thrown by
SystemCommands should be rethrown as a mentally superior team member
intervened that it would be useless.