Automatically Set/Guess Constraints
![artboard](https://cloud.githubusercontent.com/assets/420346/10946927/94aa7ec0-82ea-11e5-817e-2b4b14ed1699.png)

**Wouldn't it be great**, if, with one click, you could auto-populate the constraint settings?
Of course some manual tweaks would be needed, but this might save a lot of time.

Looking at Constraints Demo.sketch, and thinking about typical 'Mobile design' use case, some ideas:
- IF object center is closer to centre of axis then edge, then set alignment to center on this axis/' with pinning to maintain current position (negative values)
- IF object center is closer to an edge than canvas center, then set pinning to edge with appropriate values to maintain current position
- IF object spans > 90% of either artboard dimension then pin to 2 or 4 edges with current padding, non-fixed size along that/those dimensions
- Text siblings can probably have a 100% + absolute pixel padding set, per the 'Flowing text test' in Constraint Demos.sketch 
