Added IIndexable interface to support the concept of indexability
Added ReadOnlyListAnchor class and ReadOnlyListAnchorStructure struct.
Merge branch 'develop' into feature/readonly_list_anchor
Added missing comments on IIndexable, ReadOnlyAnchorList, ReadOnlyAnchorListStructure.
Removed validations from ReadOnlyListAnchorStructure
Added unit tests for ReadOnlyListAnchor & ReadOnlyListAnchorStructure.
Removed hardcoded present in the ctor validation in ReadOnlyListAnchor & ReadOnlyListAnchorStructure.
Added unit tests for ReadOnlyListAnchor and ReadOnlyListAnchorStructure.
Fixed bugs in ReadOnlyListAnchor and ReadOnlyListAnchorStructure.
Merge branch 'feature/readonly_list_anchor' into develop