added app version from package json to UI

fixes #69 and for #61

TODO
* decide where app version lives
* figure out how to show it in the help menu (i cant find the app or anyway to refer to the app so i cant connect the version showing in main menu to the application settings yet
* store the app on FieldDB.FieldDBObject?
@jrwdunham  i cant figure out how to declare an attribute in coffeescript backbone... in the defaults?