[Remote Services] Mitigate name clashes for service names

[afabiani]

Currently the name of a service, which is supposed to be unique, is built with a slugify/hashing mechanism which does not guarantee quite well that there won't clashes and conflicts when registering different services.

Improve it so that the possibility of clashes is mitigated.

WMS service names have to be unique, however they are determined from the netloc part of the service URL only and are restricted to 40 characters (the field definition in services.models.Service allows for 255 characters).

This can lead to name clashes if e.g. multiple services are available on the same network location. Examples:

http://www.lfu.bayern.de/gdi/wms/wasser/abwasser?request=GetCapabilities&service=WMS
http://www.lfu.bayern.de/gdi/wms/wasser/wsg?service=wms&request=GetCapabilities

are different WMS services using the same network location.

Suggestion:

Use the entire service URL for name determination and use all available 255 characters to avoid name clashes.