Permit test harness to use http proxy settings

This pull request permits the test harness to use
http proxy settings from both maven settings
and command line arguments.

Artifact Resolution was refactored to be contained
in a single helper class ArtifactResolverUtil.java

[FIXED JENKINS-23113]
Merge pull request #3 from scoheb/proxysupport

Permit test harness to use http proxy settings