Review scaling algorithms implementation

[bengaid]

• [ ] implement debug tracing
• [ ] ensure both viewport (vw,vh) and % unit manipulation in code
• [ ] implement abstract widgets dimensions data structure
• [ ] check if % handling by default is possible in all configurations, especially the unconstrained mode
• [ ] review impact on serialization/deserialization

[bengaid]

• [ ] recompute heights and tops when canvas size increases in unconstrained mode
• [ ] update dimensions only when edition actions done, for the action done
• [ ] use percent coordinates to avoid recompute when resize of screen
• [ ] remove css min-height and min-width. add them only for edition actions
• [ ] cleanup the code

[bengaid]

• [ ] add same size canvas for constrained mode
• [ ] in Chalk'it, keep all scaling modes