Simple job management page

Also added a seperate `job-indicator` for every job state
(pending/awaiting retry and failed)
The jobs page is automatically reloading when jobs are
enqueued, retried or failed.
Just keep the most recent 100 failed jobs + small improvements
Added specs for the HuginnScheduler
Only update Agent's last_event_at on Event creation, not when Events are updated.
Just update the job list if no modal is shown
reload to be clear
Merge remote-tracking branch 'origin/master' into event_update_should_not_touch_last_event_at

Conflicts:
	app/models/event.rb
Merge pull request #481 from cantino/event_update_should_not_touch_last_event_at

Only update Agent's last_event_at on Event creation, not when Events are updated.
Sort queued jobs by next run time, allow to queue failed jobs
Another attempt on travis bundler caching
Merge pull request #468 from dsander/job-management

Simple job management page