Added svg images
Partial: setting zoom level on svg node images
Partial : Switched out nodes and link thicknesses
Node icons are configured correctly for both selected and de-selected states
Re-factored the node select events related to input and output links
Re-factored images for events, controllers, and sensors
adding removing google zoom listener method to unpublish events.
Merge pull request #56 from mnjuhn/images

adding removing google zoom listener method to unpublish events.
Changing multiple selection key to ALT instead of SHIFT.
Changes to Sensor and Node on select
Fixed scaling on MapMarkers
Correcting multiple selection of nodes when holding down ALT and selecting Link.
clear node and links fixed
Merge branch 'images' of github.com:calpath/scenario-editor into images
Merge branch 'images' into dev
Adding method to not draw arrows on links after certain zoom level.
Fixed select toggling on Sensors
Merge branch 'images' of github.com:calpath/scenario-editor into images
Merge branch 'dev' into images
Sensor svg fixed