Export script version check

[will-moore]

As reported by @knabar and from our own experience, it's very easy for users (admins) to forget to update the script on the server to match the currently-installed version of the web app.

This can lead to unexplained errors or missing features when exporting figures.

Unfortunately the OMERO scripts API doesn't provide a way to get the version of an installed script.

However, it is possible to use the OMERO API to load the script text itself.
One option could be:

• include the release version of figure within the export script in some way that can be easily parsed from the file.
• this can be updated automatically with bump2version on release
• In the omero_figure views.py or utils.py we could add a def check_script_version(conn) that would load the first part of the script and parse out the version and compare it to the current release version.
• This function could be re-used by other tools if needed e.g. pathviewer

[will-moore]

Recent example of script wrong version causing issues: #608