Added the memory store and recall functions.

Added Ms and Mr functions. While testing noticed doing 10-ans acted like
a plus as did 10-Mr. Fixed both of these errors.
Added PI and Trigonometry buttons.

Added Pi button. Added Sin, Cos and Tan buttons. Added Inverse and
Hyperbolic toggle-able buttons. The only thing left to add is brackets
and the last button which I originally wanted to be history. It could
instead change radian / degrees or open an option menu to set such
things. I do have the Android menu button available also.