serve: link Plugins -> plugins.cordova.io
serve: refactor doFile()

Enables the functional code to be used by more than one logical branch
serve: expose plugins/ directory
serve: directory list->parent link

Normally you can browse up directory hierarchies, this was missing...
serve: Markdown files with marked

Enable README.md to be served as text/html
serve: treat various code files as text

Enable .c, .h, .cpp, .m, and LICENSE files to be served as
text/plain, because the mime sniffer defaults to forcing the
browser to download them otherwise.

Actually, code should just remove the mime type if it's octet-stream...