Documentation improvements

[viliusle]

Right now it is difficult to understand what settings you can use for Tobii config during init or what you can use on element with data-xxxxx. These are different things and supports different keys. There is info, but it is difficult to find and understand.

I suggest to create extra table for data-attributes:

• data-type
• data-target
• data-group
• data-width
• data-height
• data-controls

It would be perfect to update lib to support all options with both data attributes and inside Tobii config init. But for now better documentation would be enough. Because developers can assign data attributes dynamically (I found adding data-xxxxx attributes very tiring if you have lots of HTML)