[List] For a model, view a list of of existing custom Types and Property Groups

User Story:

"As a Model Manager I can view a list of existing Property Groups so that I can review them as a starting point to adding more, deploying them or deleting them"

Notes:

• Assuming that Property Groups as simply Aspects that have been added as dynamic models to the Data Dictionary, We need to decide whether or not to display "system" Aspects (e.g. the file system XML files) or not - it may not actually be possible to distinguish between them.
• Options for distinguishing between system aspects, dynamic models and Property Groups are:
  1. When any document is added to the Data Dictionary/Models folder, there is a folder rule that will automatically set the node type to be "cm:dictionaryModel" we could add an additional property to this type that indicates whether or not the node has been created as a Property Group or not (and then set this property when creating the Property Group)
  2. Use a single namespace for all Property Groups (e.g. "sys:" something) and then work on the assumption that any Aspects defined in that namespace are Property Groups
  3. Create a "Property Group" type and then (after the folder rule has been applied) change the type again to be the new type.
  4. Use of Public API requires entire entity structure to be defined so ACE-2182 will define the model that all subsequent REST methods will use - this is part of the reason for the large user story sizing