[RFT] Made the captcha viewhelper extending the abstract form field viewhelper
[RFT] Removed unused files due to changing captcha viewhelper to be an abstract form viewhelper
[RFT] Refactored captcha Viewhelper to act as a form field view helper.
[ADD] Add some documentation to the captcha Viewhelper.
[ADD] Change behaviour of validator so that it should reject empty values. Not working yet...