[TEST] Fixing test failures due to ordering of null keys.  In certain cases (e.g. .children) Mondrian would place members with the null keys at the end, where
the beginning of the list is expected.
Merge pull request #281 from mkambol/nullSort

[TEST] Fixing test failures due to ordering of null keys.  In certain ca...
[TEST] Adds the required signatures to the MockDialect's connection.