C++ Network Library Code

Merging from http_integration r1-r71 .

Some documentation, incomplete.

Adding default constructor and assignment operator overload to http::response and appropriate tests for http_message_test.cpp.

Adding swap and copy support (and tests) to http::request and http::response.

Adding swap support for network::message.

Simplifying message interface, removing mutable and const methods, adding unit test for copy construction, and setting the default path to '/' in case the URI is not explicitly defined in the http::request constructor - (ex. 'http://boost.org/' instead of 'http://boost.org/').

Refactored message declaration to message_fwd.hpp; Updated most files so that they now compile when using gcc's pedantic flag.

Adding support for multi-line header responses.

Adding remove_header directive implementation.

Note: Explore using CRTP/PBCP to directives and hide the message interface from the public?

Adding default User-Agent header in case a User-Agent header doesn't already exist in the request object. I also moved the test for the correct construction of an http request to http_message_test.cpp from http_1_0_test.cpp.

Note: No unit test implemented for this feature; should be doable in the Python CGI script.