File streaming

# File Streaming

This PR adds two functions $app->sendProc() and $app->sendFile() as-well as a modified call loop which is backwards compatible.

### $app->sendProc($command, $contentType = "text-plain")
This function accepts a command and optionally a content type and will transfer the output to the client.

### $app->sendFile($file, $contentType = false)
This function accepts a URI either a local file or a remote URL, you can also specify a content type as the second parameter. If left blank the function will attempt to process and find an appropriate file type.