Added keyboard search and bug fixes

Added Keyboard Search in Dropdown.
       The user can now search through the dropdown lists by just typing the name of the options. The matching option will get highlighted and the dropdown will be scrolled down automatically.

Fixed IE 8 issue.
      The dropdown menu used to close on clicking the scrollbar in IE8. 

Fixed Firefox navigation bug.
      The user was not able to scroll throught the options present in the dropdown using up and down arrow key.Fixed this issue.