Add namespace and some cleanup

[rekire]

Fixes partially #13

I just did not update the way how the gradle plugin is applied you need to do that yourself

I also removed some useless default comments, bumped some dependency versions and fixed some lint warnings.

If anyone wants to check out this fixes you can try this:

dependencies:
  // other dependencies
  imin_printer: #^0.7.0
    # remove this git part when 0.7.0 is published
    git:
      url: https://github.com/snabble/imin_printer.git
      ref: 0.7.0