Feature/387/export

Adding in structure for export capability on a feature by feature basis.

TESTING:
* Run any query (or restore an existing query)
* Click on a point, on the bottom right should be a drop down for export targets
* Select on and then click export
* GeoJSON -- Downloads the feature as a geojson file
* Google Maps -- Opens Google Maps in a new window centered on the point (you might have to disable pop-ups)

How to add in a new export target:
* Add a new component under the exports folder (see download-geojson and google-maps)
* Add in the channel you'd like the export to subscribe on

How to enable exports on a new data source:
* In the source's configuration, map the channel name to a human readable value under the exports config
* Add in the export button group HTML/CSS to the source's template
* Populate the template with the exports param from the config
* In the postRenderingAction, bind and handle when the export button is pressed

How to configure exports on a source by source basis:
* In the configuration add an additional element to the exports map
* Under the postRenderingAction, add in a new case statement for the channel name you want to support
* Body of the case statement should be very lightweight -- grab the feature and emit with the parameters the export is expecting