Control renamed to Cntrl to follow Ctype naming convention
Graphical renamed to Graph to follow Ctype naming convention
Renamed Punctuation to Punct to make it follow the Ctype naming
Renamed Printable to Print to follow Ctype naming convention

This isn't working, the tokenizer recognizes 'Print' as the built-
in 'print' and not as a class name.
Renamed Xdigits to Xdigit, following Ctype naming convention
Changed Xdigit base class to AbstractCtypeRule

It also affects one of the test cases (the empty string went from
invalid to valid).
Fixed up OneOfTest after Xdigit renaming
Updated documentation to have correct names for Ctype rules
Merge with ramaciotti/develop
Refactor rename Printable Prnt.