Add code and settings needed to include Captchas but (somehow) make it optional

[waleedmebane]

Currently the code and settings used in the online demo for creating captchas is found in the "demo-settings" branch. Move that to the "main" branch once there is a good way to make it optional.

Additional installation steps are needed to use captchas from the 'demo-settings' branch:

pip3 install 'django-simple-captcha'
sudo apt-get install libz-dev libjpeg-dev libfreetype6-dev python-dev
sudo apt-get install flite

Flite is a voice synthesis package used to provide an audio version of the captcha.