Add placeholders for undo queries.
Add quick-and-dirty undo command parsing.

Conflicts:
	You-NLP/query_parser.cpp
	You-NLP/query_parser.h
Technically, when we ask for something in either {ascending|descending} order it is actually {nondecreasing|nonincreasing} order because of the possibility of equal keys.

Conflicts:
	You-Controller-Tests/internal/query_executor_builder_visitor_tests.cpp
Add tests for the undo query.