Added a test, which sets up a job and verifies that the build state is set to unstable.

Conflicts:
	src/test/java/plugins/PmdPluginTest.java
ADDED TEST
- run_on_online_slave_and_master_with_node_restriction
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
Revert "Permit test harness to use http proxy settings"

This reverts commit 59a7c419009024860e29879e18270c27e5078a80.
Fixed installation of newer plugins.
[JENKINS-23004] Start AD plugin test(s) => 1st scenario; usage: javadoc.
Fixed installation of newer plugins.
Fixed installation of newer plugins.
Fixed installation of newer plugins.
Adapt to changes of @WithPlugin.
Improving the logic to detect the need for restart.

This avoids a lot of unnecessary restarts
Adding groovy as a dependency
Adding groovy console support to assist the test development
adding a mechanism to export local variables
Use the same set of cookies so that it sees the same thing Selenium sees
introduced useDeltaValues and changed assertTrue to assertThat
Merge branch 'ldap' of https://github.com/eidottermihi/acceptance-test-harness
[JENKINS-19614] Added a test case that tries to expose the bug.
Merge branch 'nlp_schulze' of https://github.com/sschulzeHM/acceptance-test-harness
Document Since