Layer queries and templates

[dbauszus-glx]

Layer queries should only be possible on layers.

Layer queries should be flagged as such, eg layer=true.

This prevents misuse by sending a request to a layer query template eg. geojson without locale/layer request params.

The geojson query template for example only requieres a table, geom, and qID which can all be provided as request parameter.

/api/query?template=geojson&table=mytable&geom=geom_4326&srid=4326&qID=%27foo%27

The workspace dbs will be assumed if no locale, layer connection is available.

[dbauszus-glx]

It should also be possible to query layer templates. That is a layer defined as a template which is not added to the locale.layers.