Add Pushbot instance end date to Pushbot master data table

Jacob_154284

It would be helpful for auditing and reporting to include the pushbot end date automatically to the master table of a pushbot

Jeff_146001

@Jacob_506538 I think this is a duplicate of this idea: https://community.pushbot.com/discussion/241/add-implicit-instance-fields-to-process-tables
If so, please upvote that other idea, and then confirm here so that we can delete this one.