add handling for disabling of child ordering

[lsmith77]

see http://www.day.com/specs/jcr/2.0/23_Orderable_Child_Nodes.html

in general support for child ordering tends to increase overhead in most implementations, so it may be disabled or not even supported.

[dbu]

what would this mean? detecting whether the implementation says it has the capability of child ordering and otherwise catch ordering operations and complain / have uow not check for reorderings in collections?

[lsmith77]

yes .. but also skip trying to determine changes in the sort order