Make matching on multiple members interactive, fix matching generally

[davidv171]

example:

User: !fetch david

Trup:

error: matched more than one user, which one did you mean?
1: davidv7#4226
2: davidlee#5195
3: david#5710

After this, the user inputs the index number of the target user, and trup fetches for him.

So in the case of the user inputting 1, the davidv7#4226 user would be fetched.

There have been some bug reports of matching reporting false multiple hits:

A similar user command working correctly:

Thanks to @GaugeK for the report.

EDIT: The bug report is already documented in #38

[elkowar]

iirc, @wooosh had started work on this, but never finished it. how far did you get with it / did you already have something working? this should just be implemented at some point, a general interactive member search mechanism would be very nice to have

[mlvzk]

Solved in #87