Add query filter to applications index

The list of applications appearing in the apps/index view (the root view
for errbit) can be filtered using:

 - App name eg `/apps?apps[]=Imminence&apps[]=Publisher`
 - First notice date (when the first of a series of errors was thrown) eg `/apps?from=2014-11-01`
 - Applications with active errors eg `/apps?errors=true`

https://www.agileplannerapp.com/boards/173808/cards/8007