System Information query for versions and plugins

[Draykee]

Is your feature request related to a problem? Please describe.
Right now there is no possibility to check the vendure core version and the plugin versions from a query. Plugin Versions are not even visible in the admin UI. Dealing with multiple test environments or clusters a feature to see the versions might be usefull.

Describe the solution you'd like
Plugins should return a version number. For deployment it might be helpfull, if a plugin could also read the version number from the package.json and return it.

Describe alternatives you've considered
Hard code it somehow.