Send to a Friend

Implemented the API back-end for the "Send to a Friend" tool.
Revert "Event Handling Refactor"

This reverts commit 5270de57883a658548c9f60706b0bed2dc9118fa.

Reverting as the refactor missed functionality from the old system (HTTP headers, namely).  Moreover the new error handling is backwards compatible, so there's no need to change for the application to continue working.

This refactor is therefore deferred.
Send to a Friend Fix (Keith Schema Change)

Keith changed the database schema so that the `sendtoafriend`.`when` column is no longer DEFAULT CURRENT_TIMESTAMP, breaking the API back-end (500 Internal Server Error).  Fixed this by having the server's time always be inserted.