Documentation for upgrade history and review of text

I have added better recording of the history of upgrades in JIRA. We will want to document this for 4.1 so that both support engineers and users know where to go to get the information.

Here are some sample screenshots. I don't suggest using them directly as they contain "SNAPSHOT" versions.

Also, could this text for the full upgrade history please be reviewed?

This table details the upgrades performed on this instance of JIRA. Starting with the most recent upgrade, it lists the build number which was upgraded to and the time when this upgrade was performed. For upgrades performed to versions preceding JIRA 4.1, there is no record of when these upgrades were performed.