Update rcmlserver-api/base-url in restcomm.xml through configuration

[otsakir]

<rcmlserver-api>/<base-url> configuration setting points to RVD or an RCML server that will receive notifications regarding applications. This setting is by default set to the '/restcomm-rvd' relative url.

We should support changing this from the configuration scripts and restcomm.conf so that arbitrary absolute urls can also be used.

This will help when rvd is hosted under a different domain than restcomm as is the case when using rvd as a microservice.

[otsakir]

Issue has been patched and merged.