Refactor file structure for CGI related stuff.

Move all CGI related stuff into their own subfolder to prevent directory
listing from growing even larger and to make `CgiRequest` and
`CgiResponse` classes reusable for upcoming FastCGI server API.
Disable CRLF on Windows platform.

This is common fix for CGI-programs I found from somewhere (can't
remember where) which disables CRLF-conversion on Windows platform.
Merge pull request #15 from peelonet/cgi-code-refactoring

Refactor file structure for CGI related stuff.