Feat: New method add_maven_config for JCasC config

Feat: New method add_maven_config for JCasC config

This method allows for adding settings files for new projects via
JCasC, rather than the old method of using a Groovy script to manually
add the file to Jenkins.

This also removes the __del__ function. The function was not entirely
necessary, and was causing issues with unit testing. All work is done
in /tmp, so these files will be automatically cleaned by the system.

Issue: RELENG-3893
Change-Id: I03511b9c3e1c9f9c9f79054bd6f8991cd274e8f5
Signed-off-by: Eric Ball <eball@linuxfoundation.org>