embedded entity relations & use / bug fixes

Except some fixes (see commits) the main reason for this PR is to use the benefits of embedded (sub)entities. For this for entity relations with parent have to be loaded & stored. When following a link with relation an embedded entity is now used, if available. 

Also see this commit's comment: https://github.com/zdne/SHMKit/commit/9e965f375d1a5fa163bcae2d2ef9d9bd5a30c3a5