Introduce and use new sendReply() function for LLEventAPI methods.

Each LLEventAPI method that generates a reply needs to extract the name of the
reply LLEventPump from the request, typically from a ["reply"] key, copy the
["reqid"] value from request to reply, locate the reply LLEventPump and send
the enriched reply object. Encapsulate in sendReply() function before we
proliferate doing all that by hand too many more times.