Add version.json for exposing extra api information about docker container

[nuwang]

curl http://localhost:8080/api/version

{
  "version_major": "21.09",
  "version_minor": "1.dev0",
  "extra": {
    "git_commit": "e82b50d5121c5d7b649607d816ab5a4b87ad2193",
    "build_date": "unspecified",
    "image_tag": "unspecified"
  }
}

build_date and image_tag will be populated correctly in a CI built container.

How to test the changes?

(Select all options that apply)

• I've included appropriate automated tests.
• This is a refactoring of components with existing test coverage.
• Instructions for manual testing are as follows:
  1. Build docker container and run above curl command

License

• I agree to license these contributions under Galaxy's current license.
• I agree to allow the Galaxy committers to license these and all my past contributions to the core galaxy codebase under the MIT license. If this condition is an issue, uncheck and just let us know why with an e-mail to galaxy-committers@lists.galaxyproject.org.

[mvdbeek]

Do you want to target any of the older branches ? I guess 21.09 would make sense ?

[nuwang]

Changed base to 21.09.