Improve dev docker image version usage

[cray0000]

• Autodetect used startupjs version from package.json and use that version for the dev image. Need some kind of bash semver detection for this.
• Consider possiblity of also downloading latest ./docker dynamically from github source for the used tag and find a way to cache it and to outdate it when version changes. Probably change ./docker to download and use another sh script from github master, which will be .gitignore'd.
• Setup tag building system in docker hub.
• Simplify API of running through docker. Only need 3 commands:
  • ./docker run to start dbs and enter sh.
  • ./docker exec to connect to the already running container and enter sh.
  • ./docker clean to clear the data folder in the project root, which is used by mongo to store data. Also remove all untagged images.
• Think if it's possible to improve mongo performance by having some internal docker filesystem manage the /db/data instead of fully mounting it to be accessible as files in data folder.