make thread safe

This checkin attempts to make gearman plugin objects thread safe.

src/main/java/hudson/plugins/gearman/SaveableListenerImpl.java
   Decided that this was not needed.

src/main/java/hudson/plugins/gearman/GearmanPluginConfig.java
   Added method to allow other objects to access gearman server
   launchWorker, host, and port settings

src/main/java/hudson/plugins/gearman/GearmanPluginUtil.java
   Useful utilities for this plugin

src/main/java/hudson/plugins/gearman/AbstractWorkerThread.java
src/main/java/hudson/plugins/gearman/ComputerListenerImpl.java
src/main/java/hudson/plugins/gearman/ProjectListener.java
src/main/java/hudson/plugins/gearman/GearmanProxy.java
   Made object private and added syncronized setters and getters

Change-Id: I04ca6a275ba8184bd18cf8954d07b94d02b2a47d