Should add a pragma to differentiate properties in slots and in #entityAttributes

[NicolasAnquetil]

Moose entities have properties implemented in slots, for example:

FamixTMethod
	slots: { #parentType => FMOne type: #FamixTWithMethods opposite: #methods };

and other properties imlemented in their entityAttributes

MooseEntity >> allTagAssociations
	<FMProperty: #allTagAssociations type: #FamixTagAssociation opposite: #entity 
       ...
	^ self attributeAt: #allTagAssociations ifAbsentPut: [ ... ]

when dealing with slots like in Orion, it is important to differentiate both because the first uses a slot and not the second.

I propose to put a new pragma that could be tested through a method in FM3Property

[NicolasAnquetil]

proposed name for the pragma: <isExtension> ?