Update utility

[felacek]

Pacman-esque update utility that runs every time the docker container is started. It compares hashes of each (important) file and updates the files accordingly. There are multiple scenarios (letters refer to the original, the current and the new files respectively):

• the file has not been changed between versions and the user has not altered it (X X X)
  in this case nothing is done since no update is needed
• the file has been changed between versions and the user has not altered it (X X Y)
  in this case the new file is copied instead of the old one
• the file has not been changed between versions and the user has altered it (X Y X)
  in this case nothing is done
• the file has been changed between versions and the user has altered it (X Y Z)
  in this case the new file is copied with a .new extension for the user to manually merge later, the script also outputs this into the console and writes a file with all files that need manual merging
• the original file is newer than the new one
  this happens in case the user updates their hashes or tries to downgrade to an older version of trakman, no update is performed, too bad!

The Update.js script is fairly well documented, but the user shouldn't have to run it ever anyway.

[felacek]

Closes #259

[felacek]

To test, you can try this sequence of actions:

1. go into some directory, pull the repo and checkout into update-utility, this will be the repo that you will be "updating"
2. run node Update.js to generate hashes
3. now, as a user would, change some options in some configs or whatever
4. create a new directory somewhere else, pull the repo and checkout into update-utility, this will be the repo with the "new" version
5. change some files so that this is the new version, you can change one of the configs you touched in the other repo so that there is a conflict
6. run node Update.js to generate hashes here too, including for the files you just changed
7. now go back to that first repo and update it using node Update.js ../<path_to_the_other_repo>/trakman/.hashes.json
8. if there are no conflicts, the update will succeed. if there are conflicts, it will tell you exactly what files you need to look at

obviously the user has to only care about the last step cuz everything will be done for them by the docker run script

[wsrvn]

works as intended.