Stopped using references to old global, now non-existent, caplin
namespaced classes, and switched to node.js style. In the process
introduced a new TestDefinitionRegistry which allows classes to be
overridden in much the same way as they used to be in old namespaced
style tests.
Fixed some bad member variable references
The new CSS and I18N content plug-ins are now being used in the tests
rather than the older bundler plug-ins.