fixes during PR review
empty details and 404 Not Found for internal errors about context providers
attribute vector in buildGeneralErrorResponse, but 6 unit tests fail ...
FIX 6 unit test broken in the previous commit, along with a minor bugfix in a unit test
The FIXME P9 now seems fixed
FIX 505 -> 404 NGSI error in updateContext for forward request
Merge pull request #515 from telefonicaid/task/499_network_part_of_issue

Task/499 network part of issue
Merge branch 'feature/499_basic_ctx_providers' into hardening/change_names_in_testEnv