Fix the way we add routes

[jakubfabian]

When adding a route, we need to begin with a geom string... I couldnt use a null value .. but we want an empty to begin with... fix that!

[Loisel]

I suggest the following:

1. Klick add route in wall dev view.
2. New template: Choose existing route (from spot's route list) or
   • can't find your route? Create new route
   • new view: enter route metadata
   • return to list of existing routes
3. Draw route polygon (either show the leaflet dynamically as soon as an existing route is selected or show a new view with the leaflet and a back button, I personally prefer the first option)

[Loisel]

This issue is discussed implicitly in issue 22.