Added support for stop name

[jbrown123]

I've used bitlash for a few projects and as soon as you get just a little complicated or creative you end up with several background tasks running at different times (e.g. timeouts, etc.). These tasks need to interact and it quickly becomes a challenge to manage them by slot number. Instead, it would be great if you could kill them by name.

I modified the code so it now supports "stop [*|num|name]".

Example usage

run t1, 1000
run t2, 1000
run t3, 1000
run t2, 1500

ps
0: t1
1: t2
2: t3
3: t2

stop t2

ps
0: t1
2: t3