* Fixes syntax error in usage example, and improves usage formatting
* Moves error codes into usage section
* Adds basics of geofence plugin
* Updates exports to include Geofence
* Adds geofence docs and tested functions
* Corrects promise types and comments out unimplemented functions
* Minor updates to geofence
* Reverts camera-preview changes for this branch to master
-DEVELOPER.md: Corrects 'npm run tslint' instruction to 'npm run lint'
-CameraPreview: Fixes syntax error in hide
-Base64ToGallery: Adds desc of options obj props