fix#171
Several names and HTTP identifiers are renamed to be
more consistent, self-explanatory, and concise:
* "Fields" is a collection of HTTP header fields (rfc7230 section 3.2)
* "Header" is the Start Line plus Fields. Another way to look at it is,
the HTTP message minus the body.
* `basic_fields` replaces `basic_headers`
* `fields` replaces `headers`
* `Fields` replaces `Headers` in template parameter lists
* `header` replaces `message_headers`
* `header::fields` replaces `message_headers::fields`
The changes are cosmetic and do not affect run-time behavior.
Conform to the Networking TS by renaming the Streambuf concept
to DynamicBuffer in all places. Values of types meeting the
requirements of DynamicBuffer are renamed to dynabuf.
See:
http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2015/n4478.html#requirements.dynamic_buffers
* Headers renamed
* Formal parameter names renamed
* Template argument types renamed
* Documentation updated
Vinnie Falco