DS.Model#_debugInfo()

Provides info about the model for debugging purposes by grouping the properties into more semantic groups.

Meant to be used by debugging tools such as the Chrome Ember Extension.

• Groups all attributes in "Attributes" group.
• Groups all belongsTo relationships in "Belongs To" group.
• Groups all hasMany relationships in "Has Many" group.
• Groups all flags in "Flags" group.
• Flags relationship CPs as expensive properties.