Feature/hosted-events JOINDIN-494

This change introduces an additional path to the user API: "/user/n/hosted"
Returning the events that a user has hosted (has admin privileges for).

JIRA: [https://joindin.jira.com/browse/JOINDIN-494](https://joindin.jira.com/browse/JOINDIN-494)

_This is my first contribution to joind.in, so perhaps there should be a little closer review._
Should this be a left join. I know it's pedantic and it's probably there because that's what was in getEventsAttendedByUser, but then should that be a left join either?

Just a thought.