CourtbotError Functionality Expansion

[chriswsh]

Part 1 of 2

I hope splitting these up makes code review easier.

Functionality

1. Added static wrap() utility function to wrap non-CourtbotErrors into CourtbotErrors. (This should allow updating all functions in events.js to pipakin's simpler pattern, in Part 2. The issue right now seems to be that unit testing is inconsistently enforcing functionality that's been moved to wrap(). My bad.)

Coding Practices

1. changed class name from courtbotError to CourtbotError --> constructor functions typically start with capital letters
2. Changed CourtbotError.case to CourtbotError.casenumber to avoid potential reserved word conflicts.
3. Added backwards compatibility for CourtbotError.case; however, case is no longer an enumerable property. (Can we get away with dropping case?)