Removed the check on content-type from JsonRpcServer.php

 I needed a version of jsonrpc that does not check content-type.
 I know that such behavior is not within the JSONRPC standard but there you are.

 This will be used in an app where we do not want to mess with pre-flight
 and using an innocuous content type is the best way we have found to stop pre-flight.

 I will have the caller of Service::start add Access-Control-Allow headers before
 anything else gets started.

 So, apologies to the author of this code for making it a bit of a hack

 TODO - come back and make it check for the content-type we ultimately decide to use

 As a second hack/change - have Service::start actually echo/print the jsonized response
 rather than return it to (presumably) an index.php file