Fulltext search refinements

* enable empty query `q=&...` to return all visible objects (or counts
  therof)
* include `NULL` in list of visible contexts
* enable `counts_only=true` query parameter to return the count of
  matches per type
* deduplicate `results.entries`
CSS update for controlobjective icon set
CO icon added to styleguide
Merge pull request #80 from reciprocity/feature/control-objective-icons

Feature/control objective icons
Update AppEngine SDK 1.7.6 -> 1.8.1
Refined show/hide of "Map to this object" link in sidenav extended info
Story 52269321: Mapping from lefthand nav objects to page object
Basic mapping support for more object types.  Directive-to-Control throws not implemented error.
Merge pull request #81 from reciprocity/feature/update-appengine-sdk

Update AppEngine SDK 1.7.6 -> 1.8.1
affix display fixed, added brackets on program page display
added oneline and fixed font size
widget handlebars updated
top header actions fix
pushed info to the top, added brackets to all tabs
Track changes to multiple objects
Add behave tests for event and revision logging
Merge pull request #82 from reciprocity/feature/sidebar_object_mapping

Mapping of lefthand nav objects to page object
Merge branch 'release/0.9a6'
Merge tag '0.9a6' into develop

Sprint 6
added handle on object nav