[Demo] fix auto load values switch

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Demo] Use Liquid delegate on demo app

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Demo] Fix bgColor variable name

It was set to `textcolor` instead of `bgColor`

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>
[Enhancement] Only send a variable one time per session

Each time a variable was used in development mode, it was being sent to Liquid server to ease configuration process.
Now, each variable is only sent one time per session.

Signed-off-by: Miguel M. Almeida <miguelcma@gmail.com>