Turns out that having these pop up on every tab-press is really annoying,
and you usually only want them when it didn't manage to autocomplete anything.
The +command-parser must now produce both a flag and a command noun.
If the flag is true, instantly runs the command from the noun.
If false, maintains standard behavior and only runs it on-return.
Deals with sole events, deferring to the underlying app only for higher-
level sole-handling logic.
Currently doesn't offer fancy printing logic, but can easily be extended
to do so.
Passes sole-ids on to the underlying app in all arms so that it may run
session-specific logic wherever it desires.
