adding debugger support
improved the robustness of the code that waits for the build to start
Coming up with a factory to launch Jenkins

... including an implementation that pre-launches Jenkins to speed up testing
Push the configuration of JENKINS_HOME down so that multiple controllers can be initialized concurrently.

 Updating the current environment can cause a race. Tomcat and JBoss controllers currently do not support cached prelaunch anyway because they assume a fixed CATALINA_HOME.
Capybara does not support concurrent use, so the code we use for prelaunch cannot touch it.
exposing the PRELAUNCH option.

The intent is to make this option work orthogonally with any
JenkinsController, but as it stands now it can only work with
WinstoneController.