Clarify restrictions on OrderedMember. Fixes #574.

[rjyounes]

Change:

owl:unionOf (
	[
		a owl:Restriction ;
		owl:onProperty gist:precedesDirectly ;
		owl:someValuesFrom gist:Thing ;
	]
	[
		a owl:Restriction ;
		owl:onProperty gist:followsDirectly ;
		owl:someValuesFrom gist:Thing ;
	]
	[
		a owl:Restriction ;
		owl:onProperty gist:sequence ;
		owl:someValuesFrom xsd:integer ;
	]
) ;

to

owl:unionOf (
	[
		a owl:Restriction ;
		owl:onProperty gist:precedesDirectly ;
		owl:someValuesFrom gist:OrderedMember ;
	]
	[
		a owl:Restriction ;
		owl:onProperty gist:followsDirectly ;
		owl:someValuesFrom gist:OrderedMember ;
	]
	[
		a owl:Restriction ;
		owl:onProperty gist:sequence ;
		owl:someValuesFrom xsd:integer ;
	]
) ;

This change clarifies the meaning of the restriction, though it is strictly speaking logically redundant: since only OrderedMembers belong to OrderedCollections, precedence would be only in relation to other OrderedMembers. There's an edge case counterexample where an OrderedMember is asserted to precede or follow something outside the OrderedCollection, but it's hard to see how that situation would occur. At any rate, this creates greater clarity.