improve AR::all_models for non-eager-loading

include namespaced models, and move two models to where
they actually belong

Change-Id: I8f5940d927e4d1fb2b05fceeca121c04d4de47d5
Reviewed-on: https://gerrit.instructure.com/37447
Tested-by: Jenkins <jenkins@instructure.com>
Reviewed-by: Brian Palmer <brianp@instructure.com>
Product-Review: Cody Cutrer <cody@instructure.com>
QA-Review: Cody Cutrer <cody@instructure.com>