Provide TRUE and FALSE as public static LazyNumbers

[mmorrisontx]

Implementing custom boolean LazyFunctions is a bit annoying at the moment, because each function (or project) needs to maintain its own copy of ONE and ZERO (similar to the example).

If EvalEx exposed a public LazyNumber instance for TRUE and FALSE (or ONE and ZERO?), it would make implementing custom LazyFunctions trivial, and in most cases they could just be a lambda.

[mmorrisontx]

Alternatively, a simpler abstract implementation of LazyFunction which needed a long lazyEval(lazyParams) rather than a LazyNumber lazyEval(List<LazyNumber> lazyParams), would also solve the problem.

[uklimaschewski]

Obsolete with version 3