Task/499 network part of issue

### Description
o Fixed the 'network part' of issue #499 (part 1 of uncached queries/updates for context providers).

o About adding CB_PORT as preferred variable to BROKER_PORT, doing the FULL change, i.e. completely stop using BROKER_PORT etc is a too big task to include in this PR. I tried but it got BIG. Coming in a PR soon.

o About statistics, I have passed completely on the statistics in this PR. There are two new messages 'QueryContextResponse' and 'UpdateContextResponse' but they are NOT included in the statistics. Perhaps this was not a good idea, and it is easy enough to include them. However, I have a feeling the entire statistics concept needs to be looked over ...

o I had some problems with the compiler copying entire vectors, in the clone/fill functions. I changed a few of them from 'const Class&' to 'Class*'. Also, I changed the name 'clone' to 'fill' for the methods that don't actually clone anything (methods that just fill).

Deferred to issue https://github.com/telefonicaid/fiware-orion/issues/523