Use shorter action route url

[ZakarFin]

These both work as server endpoints and do the same thing:

• https://demo.oskari.org/action/GetAppSetup
• https://demo.oskari.org/action?action_route=GetAppSetup

I think we should update the codebase to use the shorter form (check that frontend/server doesn't bake in the action_route= in front of the route to call. The config that oskari-ext.properties have by default is currently this:

# url path to call for ajax requests/action routes
oskari.ajax.url.prefix=/action?

https://github.com/oskariorg/sample-configs/blob/4c6c3a48d879a8264dfa9ad0798aff4f4217e24f/jetty-9/oskari-server/resources/oskari-ext.properties#L48-L49