Improvement to systemCheck

I've made some improvements to systemCheck:
* No more ugly prints, this way prints the messages in the original way and works in Python 3.
* Removed pyQT check, there will be no GUI in 0.5 right? so it's useless.
* Tesseract is not a mandatory component so I've put it as an improvement and not as an error, also I've changed the description.
* Small typo fixes.

If you agree you can merge.