Hide namespace presenter for stable push.
Allow creation of MethodSubjects for Newspeak source from MethodReference until separation of namespaces (unbreaks browse-it).
Merged from main
WIP on generalized Mixin application. Deliberately broken while investigating VM crash. Appears to create correct mixin and class structure.
WIP. Fixed code that caused VM crash. Tests for pure mixin application classes pass (shows need for more tests). Using generalized mixin applications in superclass clauses does not work yet.