Remove all non-default pattern engines once stable

[bmuenzenmeyer]

Alter getSupportedTemplateExtensions() to look for node_modules/patternengine-node-* instead of its current mechanism

[bmuenzenmeyer]

now managed in core

[geoffp]

While this is true -- I just found template renderers (rather than engines) hanging around in the edition! This issue seems close enough to me. Removing them.