Extend the replacement rules of *.alias files

[kantholtz]

Currently commands like t a do not work correctly because the specified rule t a [0] : tmux attach -t [0] is not able to handle the case that [0] might not be set. It should be possible to extend the syntax of the rules in a way where additional information can be enclosed in the replacement rule.

Proposal:
t a [0] : tmux attach [-t 0] yields tmux attach for t a and tmux attach -t foo for t a foo.
The replacement regex would look something like this: \[([\w-]*)(\d+)([\w-]*)\].

[kantholtz]

Also, allow repeating switches - e.g.: c j [0] -> journalctl {-u 0} -b where invoking c j foo bar translates into journalctl -u foo -u bar -b.