CIMI - Add support for $expand on cloudEntryPoint with refactoring input from Michal Fojtik.

This pull request is for Add support for $expand on CIMI cloudEntryPoint.
It addresses Jira DTACLOUD-502

It includes changes needed to adapt to using a hash to contain all root entry
point, vs the acts_as_root_entity method and some refactoring based on input
from Michal Fojtik.
Huge Thanks! Michal Fojtik!

There is one outstanding issue: the credentialTemplates is erroneously
listed as a root entity. Hopefully reviewers will help shed some light on this.
I will also continue to investigate.