Uha calculator new

[DracoTempus]

[eloyzone]

Thank you for contribution and your attempts.

I reviewed your commits, but please fix the following issues:

1. I cannot figure out the difference of "Cancel" and "Clear or C" buttons, they have same behavior. (It's better to have one button to clear all inputs and one button to clear the history section)
2. C and Cancel buttons does not look good.
3. remove irrelevant comments.