Basic Calculator: Process operations of a calculator

New argument is added to the init method:
 - $options argument is added to allowed user customization.

New method is added:
- bip() method to produce sound on error

Bugs fixed
- Start new operation without initialization
- toggling equal key result to an addition to the last result
- a calculation result can not be backspaced. Backspace toggling several 
  time on a calculation result wont produce anything.
- The sign of the output result can not be changed by single click even by 
  toggling the sign key.
- key press event is now cached by the input field to avoid focus lost.

Code structure change:
- objects properties are valuable renamed to suit the coding purpose.

Change of the graphical representation:
- The calculator graphical interface (UI) is redesigned with the latest HTML and css
  version (HTML 5 and CSS3).