Make the parsers and patterns comply with MSRP formal syntax

[tuijldert]

As an example, the content stuff pattern matcher doesn't exactly comply to the
token defined in MSRP RFC.
Make all of the parser patterns comply.
When setting values that are specified on the RFC such as content-type and others,
make sure that they comply to the RFC's formal syntax, otherwise, send an
exception, avoids incorrect use and parsers misfunction