Allow a consistent defaulting mechanism for picking up the Jenkins under test and the plugins.

The sequence is:

- Follow JENKINS_WAR environment variable
- Try WORKSPACE/jenkins.war
- Try $(pwd)/jenkins.war

The plugins used will try for the first of:

- Follow PLUGINS_DIR
- A sibling directory of the resolved jenkins.war that is called `plugins`
- Try WORKSPACE/plugins
- Try $(pwd)/plugins
Don't litter the file system with temporary files
Make the pom.xml behave more like a regular maven pom. Until we get a better cucumber driver we this causes a bloat in profiles. Need to investigate writing a cucumber provider for surefire
Oops!
Add back defaultsTo
Tidy up resolving to a more standard pattern
typo
Better control of the JVM used to launch Jenkins
Don't add the credentials if they are there already
Better error reporting
Battling to keep files in sensible places
Battling to keep files in sensible places
Make sure the correct effing ssh key is selected for each slave
You better be effing escaping any paths that are borked