Need an interface for triggering a JIRA backup and restore

When performing a workflow migration, JIRA says:

Note: You are about to begin a process that will change every issue in project XYZ. This process can take a long time, and therefore it is advisable to perform this operation when the system is under low load. Please ensure that you have a backup of your data before proceeding. If the process fails or JIRA is shutdown before the process completes, you can attempt to associate the workflow scheme wfs2 with project B Project again. If the process fails again, please restore from backup to ensure that issues in the project remain in a consistent state.

Although this warning won't apply to most Studio customers with small JIRA instances, we have a few larger instances, and to use JIRA safely here requires being able to perform backups. We should have an interface for (at least) triggering an XML backup in a hardcoded directory.