Add native optimizations

[cirospaciari]

These methods need native optimizations:

• App#get_headers
• App#get_queries
• App#get_parameters
• App#preserve
• App#cork_end
• WebSocket#cork_send
• App#send (end + content-type + status + other headers + cork)
• static file serving needs to be all In native (C++) without touching python at all.
• sendfile must be all native too.