Large revamp of host filtering

* The filter content is now passed as a JSON string between web2py and the ui.
* Clear Filter does what you think it should now
* Fix pagination when filtering on an Engineer
* Added booleans for accessed and follow up
* Fixed a number of additional bugs
* Removed address range since it may never be implemented
* Additional little tweaks to UI
Merge pull request #109 from grutz/filter_fix

Large revamp of host filtering