JIRA installer ships with JRE, lacking JAXB default implementation

So, I use the JDK for all installs, most users I have also use this, the JDK comes with a jaxb reference impl as part of tools.jar. The JIRA installer ships with a JRE lacking tools.jar. This means users who using the installer encounter runtime exceptions if addons used JAXB and didn't add their own implementation jar.

• https://thepluginpeople.atlassian.net/browse/JEMH-2544

Bamboo had the same thing: https://jira.atlassian.com/browse/BAM-12484

It would be 'useful' if the JRE bundled with the JIRA installer had the referred JAXB impl jar.

I've added this into my addon, however, users upgrading are in a catch22, as it breaks startup before they can upgrade.