illegal characters '$()' no longer lead to faulty output

checks are added for these three characters, as they
indicate shell functions '()' or variables '$', which
are not convertables, as the iptables_converter does
not interpret anthing in input file.
short inputfile should be valid except for a variable

as this file contains shell variables, indicated by a
leading '$', they are not valid as input. needed for
test and proof.
short inputfile should be valid except for a function

as this file contains shell functions, indicated by a
'(' or a ')', they are not valid as input. needed for
test and proof.
Thanks: Guido provided debian bugreport #748638
tests now proof for shell varaibles and functions

error message and exit value (1) are verified
manpages updated and corrected for exit status
copied and adapted from iptables-converter
version set to 0.9.5
ip6tables_converter.py added
adapted to additional tests for shell vars, funcs
sphinx-doc updated, errors with functions and variables mentioned
version changed to 0.9.5
closes #748635

control now reflects in a better way behavior and purpose
version changed to 0.9.5-1, closes #748638