tunable unqualifiedPathStepPolicy seems unnecessary - deprecate it

The tunable unqualifiedPathStepPolicy seems unnecessary

This policy can be based on the elementFormDefault of the lexically enclosing schema where the path appears.

If the elementFormDefault is unqualified, then a path step with no prefix should be assumed to have no namespace.

If the elementFormDefault is qualified, then a path step with no prefix should be assumed to be in the default namespace (if defined) and no-namespace if no default namespace is defined.

These correspond to the unqualifiedPathStepPolicy values of noNamespace, and preferDefaultNamespace respectively.  The default for unqualifiedPathStepPolicy is noNamespace which would correspond to the elementFormDefault default value of "unqualified". 

The third value of unqualifiedPathStepPolicy, which is "defaultNamespace" is problematic because the schema may have none.