Plugin version information

[FauxFaux]

Many plugins have $Rev$$Date$ as their version, as git isn't doing keyword replace. I'd rather it wasn't. We can:

• use maven filtered-resources to add the revision (probably?)
• Indicate whether plugins are loaded from choob-plugin: #393 and use the bot version (which we don't actually know; again, build step) as the version
• Show the git hash-object of the plugin, as it was loaded, as the version? Or implement some of git describe, i.e. number of seen revisions with different hashes since the running version's tag, or something.

That, or just purge all the revisions back to "HEAD" as nobody actually cares.