Remove a judge's votes when they are unassigned

[robmcl4]

adds backend support for deleting a judge's votes if they're removed from a show

TO DO:

• [x] Add modal to front-end warning of this

[robmcl4]

Added warning modal. Ready to be reviewed.

[billdybas]

@robmcl4 I'm going to merge this and mark the caching issue as a known issue.