Include event name in overlap message

[slominskir]

Fixes #62

[slominskir]

Currently we rely on DB constraints / triggers to do the checks and they simply report when an overlap occurs. We need to add custom app-level queries to actually figure out what specifically overlapped.

There are a few cases that need to be checked to see if overlap is introduced:

1. Adding a new Event (that starts within bounds of an existing event)
2. Editing an existing event to update timeUp
3. Editing an existing event to update type
4. Adding a new incident that moves event timeDown earlier
5. Editing an existing incident that moves event timeDown earlier