Our initial implementation of `bar { }` assumed that the commands could
only be used in the config. This is not true for two commands:
* bar mode
* bar hidden_state
This patch makes it possible to issue these commands outside a bar
block, for instance through swaymsg
$ swaymsg bar mode hide bar-0
This does not implement the `barconfig_update` IPC event which should be
trigged from these commands. I have added TODO's where this should be
added once implemented.
a96a5e0013