Add simple keys for using different functions

The calculator in elementary OS could be made more convenient to use by adding keys for different functions such as the square root. Entering "sin" in the calculation field could be done by pressing "s" instead of clicking with the mouse and so on; "q" for square root. Also important constants such as pi "p" and e, "e" should be added to make the calculator actually useful.

The keys could be marked on the operator buttons, so that the keys are obvious without reading the help file. I also propose that the 8 and 9 keys on the top row give parentheses if Num Lock key is pressed.