changed default proposal; now its one change plus coin flips with probability self.propose_p
improved testing
see MAJOR-CHANGES; reworking proposals, primitives
Merge branch 'master' of https://github.com/piantado/LOTlib
Merging with main branch, weird thing with Primitives/Number.py.
Finished initial JoshModel.lot_grammar; JoshModel grammars have not been tested yet.