* This adds "str.expandtabs", "str.translate", "str.ljust",
"str.rjust", "str.center", "str.zfill", and "str.splitlines".
* While these are barely performance relevant, it's nice to have
one type, str, complete at least.
* Firstly , add all methods with no arguments, as these are very generic
to add, introduced a base class for them, where we know they all have
no effect or raise, as these functions are all guarantueed to succeed.
* This covers "str.capitalize", "str.upper", "str.lower", "str.swapcase",
"str.title", "str.isalnum", "str.isalpha", "str.isdigit", "str.islower",
"str.isupper", "str.isspace", "str.istitle" functions.
* Also add support for 'str.index', 'str.rindex' which is very similar
to 'str.find', just may raise an exception.
* Also add support for 'str.split' which will be used sometimes for code
needed to be compile time computed.
* Also add generated test to cover all str methods easily.