Renamed boolValueParserTests.java to keep Java coding standard.
Added implementation and tests for the factory to create value parsers.
Made the ValueParserFactory more like an actual factory with a static method, and less like a visitor.
Implemented isEqualTo and equals on all the value classes.
Added boolean operations to the Bool class.
Added integer operations.
Added a skeleton for the InterpreterVisitor class.
Added tests for atomic expressions.
Added implementations for atomic expressions.