Added test for parsing nested tuples and lists in for-statements
Added parsing of nested tuples in for statements
Added test for type inference from nested tuples to index variable of for-statement
Removed unused types field from GeneratorExpr and parse_for_index_variables
Added test for nested tuples in generator expressions
Added semanal test for nested tuples in generator expressions
Added type checker test for nested tuples in list comprehension
Fixed testSimpleListComprehensionNestedTuples2
Merge pull request #479 from spkersten/nestupfor

Nested tuples in for-statement's and generator expression's index