Cleanup of ABNF, DCG and HTTP modules.

* [DCG,SC] Big reorganizing of DCG modules.
* [RFC2616_ABNF,RFC4234_ABNF,SC] New modules containing the DCG implementation of ABNF rules.
* [RFC2616_BASIC,RFC4234_BASIC,SC,DOC] New modules containing the DCG implementation of basic rules defined for ABNF.
* [HTTP,SC] Planning to rename all HTTP modules to their corresponsing RFC.
* [HTTP_URL,SC,DOC] New module implementing HTTP URLs.
* [HTTP_VERSION,SC,DOC] New module implementing the HTTP version field.