Error location for all compilation errors

All exceptions raised during compilation due to compilation errors now contain positional information about the error in the source code. This was missing in particular by various causes of UnknownIdentifierException as well as UnknownTypeException. The changes are reflected by the accordingly modified ("negativ") test cases, namely neg_Function* and VariableAccess*.

This feature should help developers writing larger Monty applications for obvious reasons and also allows for easier development of a possible future Monty IDE (think error/syntax highlighting).
You could call ```this(null, identifier)``` to avoid code duplication.