Version compliance / validation for JAXb based project import

Formally, we do not support projects created with newer versions of Jalview imported into an older version. Prior to release 2.11.0, this situation rarely happened since older versions of Jalview used Castor, which enforced strict schema compliance.

Since JAXB does not enforce compliance a UI component will need to be shown warning users when potentially incompatible projects are imported rather than relying on the 'if an exception occurred, project import failed' logic currently in place.