Add % ease values to applicable patterns

[scantopattern]

We have established percentage ease which allows scaling of the sweatshirt block to adjust ease to the size of the person, allows sweatshirt to be scaled for children as well as fitting a wider range of adult bodies.

[aharwood2]

Where ease is a fixed value, we should change it to a percentage based system based on another measurement. This could be a quite a complex piece of work to retrofit to all patterns so we can hold off on this for now.