LP#1410369: Create user messages when configured to do so

LP#1410369: Create user messages when configured to do so

When an A/T definition has both message_usr_path and message_template
defined, we gather the user, sending lib, template, and title and push those
into the environment.  After the user-defined reactor has successfully run,
we pass the environment off to a special-purpose handler that generates
output for actor.usr_message.message and, upon success of that, we insert
the user message into the database.

Signed-off-by: Mike Rylander <mrylander@gmail.com>
Signed-off-by: Galen Charlton <gmc@esilibrary.com>