Replaced SourceCodeInformation hierarchy by simple class
More refactoring in the AST package
Removed some more syntactic noise from the class and function namess
Made AST classes final where possible, because I want people to extend from those. If people want to add AST nodes they should extend one of the abstract classes and not the concrete ones.
Removed SymbolTable interface
Renamed SymbolTableImpl to SymbolTable as there is no interface anymore. Feared to do this in one step because of the Git catastrophe of two nights ago.