NGSI10 Subscriptions with ServicePath

### NGSI10 Subscriptions with ServicePath

Now ngsi10 subscriptions support Service-Path. Just one service-path; if more than one is sent in the subscription request an error is returned.
Complete with functional tests.
 
Fixes issue #675 (as the name of the branch indicates :-))

"all entities" use to mean isPattern=true and ".*". Although your wording is correct, I think it would be clearer to include "#" after /Madrid. Ok, it's redundant... but I think that in this case redundancy helps and avoids possible confusion (in my case, I was confused).