tripel_core: CategoryNode.create_new_comment_node became CategoryNode._create_new_comment_node, with public wrappers for creating new threads and replying to existing comments; renamed VIEW_METASPACE_COMMANDS to VIEW_METASPACE_COMMANDS_ACTION; perm check functions now take db_tuple instead of pgdb.  tripel_web: updated perm check calls to send DB_TUPLE instead of PGDB, added stubs for page classes for comment and writeup creation.  tripel_tests: updated is_allowed_to_do calls to send DB_TUPLE_PT_NM instead of PGDB_TEST.