Added new functionality to the filters

- users can now search on attributes
- attribute search returns any event that has a a sub-string match on the entered attribute
- can also be used to negate (e.g: don't show me any events that have a sub-string match on any of its attributes)
Quick filter tool, some further tweaks to the filters

- quick filter on the event index
- finds events with a sub-string match on event info, orgc, attribute value, attribute comment
Version pushed
Merge branch 'hotfix-2.3.20' into develop