Add new configuration flags to simplify the customization process
of the virtual keyboard.

- lang-<code> flag enables the specified language.
- lang-all flag enables all the languages.
- handwriting flag enables the handwriting input method (t9write
  or lipi-toolkit)

Updated test cases and also fixed the virtual keyboard for single
language support.

Change-Id: I599816bed591bd193ad26cef0e9bf4812146e865
Reviewed-by: Oswald Buddenhagen <oswald.buddenhagen@theqtcompany.com>
Reviewed-by: Mitch Curtis <mitch.curtis@theqtcompany.com>