* Remove set layout style size helper
* Update API to set and get a CGSize / ASRelativeSize from an ASLayoutElementStyle
- Expose ASRelativeSize type
- Add new helper properties to set a size / relative size to ASLayoutElementStyle
- Don't expose the size in ASLayoutElementStyle anymore and move into ASLayoutElementStylePrivate
* Update examples
* Update comments for size helpers
* [Layout API] Rename ASLayoutable to ASLayoutElement
* arg
* fix wrapperWithLayoutElement
* [Layout API] Rename ASLayoutable to ASLayoutElement
* arg
* address Michael's comments
* Remove ASLayoutValidation files that were deleted on master since this diff was created.