Fix bug in string formatting

Plain " in a string should be slash-protected.
Add support for the ord intrinsic
Fix return_alias implementation
Add replace method from str module

This unlocks euler22 and eulereuler42 :-)
Rework class hierarchy in intrisic.py

So that function intrinsic can also have a combiner.
PEP8 compliancy
Fix bad interaction between combiner and empty lists parameter

Previous code might result in AugAssign on an empty ist, which is
undefined in pythonic.