Add onClick creation of ROIs

Closes daiquiri-tomo#37 (closed)

This MR adds a click interaction to add new "scan task" ROI. It also fixes the TomoTiling styleguide demo.

The onClick is provided by a dedicated PointerClick component. I first used the click event but I had issues with the other interactions, so I implemented on click on top of the pointer events (I'd take any simpler approach).

attn @bocciare