Clean up C++ code

Joshua Goinsrequested to merge
work/redstrate/code-pass into master

Just in time for kdereview, here's a big bloc of changes to remove the cruft:

  • Bring up the C++ code to rest of KDE standards (explicit constructors, const, QString forwarding, etc)
  • Remove the leftovers of pre-SDL2 code like evdev headers
  • Remove most of the debug messages, and leave the useful ones as qWarnings
  • Make sure all of the models are using the proper checks
  • General cleanup

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