[Fixes #674] Loading embedded relationship in sideloaded relationship
fix for embedded records not being loaded when their parent is sideloaded
Clean up relationship invariant maintenance tests
Make BasicAdapter test more resilient to failure
Correct association in embedded save test
Materialize record before triggering hooks

This resolve #405.
Merge pull request #709 from ghempton/sideload-embedded

Fix for loading embedded records who's parents are sideloaded
reject save operations when record is invalid or has error