Move component props into separate files

[matteason]

Some components are reused frequently (hint, error message etc). Move their props out to a separate file so they can be included in other components' prop lists easily without having to redefine all the props. Consider doing this for all components to improve experience for consumer apps that may want to wrap other components

[matteason]

I'm not sure this is possible with how docs are generated at the moment.

We use vue-docgen to parse props from components, which does static analysis and doesn't follow imports etc. It would be great to be able to do this in the future but it would probably require an enhancement to vue-docgen