Hardening/libcurl

**DON'T MERGE**

Orion uses libcurl to send HTTP requests.
The .spec needs to be modified to include dependencies with libcurl-devel (for building) and libcurl (for running). Wiki documentation about CB requirements should be also modified to include a release note for 0.14.1 explaining the new requirement (see https://forge.fi-ware.org/plugins/mediawiki/wiki/fiware/index.php/Publish/Subscribe_Broker_-_Orion_Context_Broker_-_Installation_and_Administration_Guide#Requirements).

@LeandroGuillen , are you brave enough to modify the .spec :)? Or prefer me doing that?