Tweaked test. No functional change intended
PluginCollection: keep plugins that return an empty array
RendererGenerators\PHP: added support for namespaced class names
PHP renderer: omit its source for serialization
Renderers\PHP: preserve custom properties during serialization
RendererGenerators\PHP: do not create the getParamAsXPath() method if it's not used
TemplateHelper: adopted asXPath() for easier reuse
Changed the behaviour of stylesheet parameters to be static by default