RegularExpression class was not wrapped to JS RegExp.

(the one that was loaded with methods did not match
with the one wrapped during boot,
because superclasses were different)
Merge pull request #343 from herby/fix-regexp

RegularExpression class was not wrapped to JS RegExp.
Renamed ASTDebugger to ASTSteppingInterpreter
Refactored ASTInterpreterTest
First test in ASTSteppingInterpreterTest
- Small ASTInterpreter refactorings
- More interpreter tests
Removed a console log:
Beginning of an ASTDebugger
More changes to ASTDebugger