Use a real event for reload notification

Don't rely on the hacky state.allLoaded variable, but us a $rootScope
event instead.
Add fn to replace state through a single call

As in moving to a next sentence in a document. Triggers a stateReload
event.
Add navigator Ctrl and service

Very very simple right now, subject to change once a second (slightly
different) retriever is tried out.
Use navigator in treebankRetriever
Minor restyling of NavCtrl html
Refactor navigator service
Extract navbar to a directive
Minor update of navbar1 template
Add some toggle vars in navbar directive
Add configuration for navbar in staging conf
Make showing of navbar and search configurable
Minor formatting
Don't use locator service for now
Add resource factory
Use resource factory in treebankRetriever
Fix SearchCtrl spec
Make resource a factory-like service

Check the comment in resource.service.js.
Add configurator.provideResource

Provides a new resource object retrievers (and savers) can later on use.
The configuration of this object is currently a little hacky.
Add conf setting for retrievers

They are used to configure our resource objects
Use resource in treebank and bspMorphRetriever