CMakeLists: altered requirements: Bison 3.0.0 should be enough
ondriks_mtbdd: add stubs of methods for renaming and projection
ondriks_mtbdd: add first version of Project()
OndriksMTBDD: fix a bug in Project

It used to fail when the result of projectInternal() was not an internal node.
SymVarAsgn: fix a bug in getAllSymbols()
OndriksMTBDD: add implementation of Rename() (+tests)
OndriksMTBDD: add some invariant checkers to Rename()
OndriksMTBDD: add operators == and !=