Deleting an Entity should delete its associated events

[lspxxv]

Deleting an Entity should include its associated events so stale events aren't still hanging around when the parent entity has been removed from monitoring.

Feature Suggestion

Customer comment - It helps keep the event database clean and we don't have to write external scripting to parse the event list and figure out what is stale...

Possible Implementation

Context

internal ref - https://secure.helpscout.net/conversation/2129763947/30718?folderId=4465878

[asachs01]

Resolve vs. delete events? We have customers who have use cases (like decommissioning nodes/hardware) where they would want a decommed entity to no longer have associated events. @portertech is thinking it would be a separate API.

Two cleanups here:

• Entity doesn't exist, events should be cleaned up (could there be a /decom endpoint?)
• Check doesn't exist, events should be cleaned up (there's more here that would need to be fleshed out)