Changed Site / SiteApi to be separate neko files

The aim here is to have:

 * Site -> server/index.n (the web site, no remoting calls processed in this module^)
 * SiteApi -> server/api/2.0/index.n (accepts remoting calls)

(^) Note: Remoting calls sent to this URL though ("lib.haxe.org/") will be mod_rewrite forwarded
    to legacy/index.n

Any future backward-incompatible API changes should have a new API version number and endpoint.