[MONDRIAN-1727]  Dimensions with a closure table have an additional hierarchy, which was causing failures in cases where the default hierarchy is being retrieved.

RolapHierarchy has a "closureFor" field which formerly was always set to null.  This change sets the value when appropriate, and uses it to filter out closures
when determining which hierarchy is the default.
Merge pull request #154 from mkambol/closureFor

[MONDRIAN-1727]  Dimensions with a closure table have an additional hier...