Allow killing of multiple modules at once

[TheTechromancer]

Addresses #1391.

[codecov]

Codecov Report

Attention: Patch coverage is 40.00000% with 9 lines in your changes missing coverage. Please review.

Project coverage is 92%. Comparing base (1461128) to head (c46de79).

Files	Patch %	Lines
bbot/cli.py	10%	9 Missing ⚠️

Additional details and impacted files

@@          Coverage Diff          @@
##             dev   #1480   +/-   ##
=====================================
- Coverage     92%     92%   -0%     
=====================================
  Files        327     327           
  Lines      21112   21109    -3     
=====================================
- Hits       19380   19361   -19     
- Misses      1732    1748   +16     

☔ View full report in Codecov by Sentry.
📢 Have feedback on the report? Share it here.