Implement static class access

[Brofian]

In the case of static properties, the class identifier is wrongly detected as a VarRef. For example:

String numAsString = String.valueOf(34);

is currently evaluating the expression on the right as

MethodCall(VarRef(String),valueOf,List(Literal(34))

In this case, String is used as a reference to the static context of the java.lang.String class. The parser has no way of knowing that, the typeCheck can test this against all known variables and all known imports, but this should not be necessary to do in the bytecode generation.

My solution would be:

1. Create new AST Node StaticClassRef(className) that is not used by the AstBuilder
2. Once the TypeCheck encounters a VarRef towards an unknown variable that starts with an uppercase letter, it can convert it into a StaticClassRef
3. The Bytecode generation can then include a special case for accessing static class members via their static context