Intoduced sanitize_arguments hook in commands

I think we sould be defensive in commands to avoid that some invalid
argument splits into the business logic (aka request, response, ecc...)

`sanitize_arguments` must be used to escape, chop, nomalize all
arguments before those arguments are used to created the command and
possibly raise an exception or a warning

Moreover, this method is easily unit testable and it should be since
most of the issues could be related with input sanitization and
validation
Removed dead code
Refactoring: simplified logic