ENH: Sort ExtensionWizard.py --listTemplates

Change TemplateManager.listTemplates method to sort the list of
templates per category, rather than outputting in the semi-arbitrary
order of dict. (The categories come from a list, which retains the
declaration order - which is likely to be a meaningful, semantic
ordering that is at least as good as a lexical sorting - and so do not
need to be sorted.)