DMV - update measure extraction query for CL < 1200 (#98)

Updated the DMV measure extraction query to exclude all measures where MEASUREGROUP_NAME (TABLE_NAME) is empty, instead of explicitly excluding only measures where name is "__Default Measure".
This update will also exclude the "__No measures defined" system measure that exists in data models with compatibility level prior to 1200 (verified in PowerPivot with a compatibility level 1103)

Author: albertospelta

src/Dax.Model.Extractor/DmvExtractor.cs

@@ -368,7 +368,7 @@ KPI_TREND AS KPI_TREND_UNIQUE_NAME
     MEASURE_UNIQUE_NAME,
     [DESCRIPTION]
 FROM $SYSTEM.MDSCHEMA_MEASURES
-WHERE MEASURE_NAME <> '__Default measure'
+WHERE TRIM(MEASUREGROUP_NAME) <> ''
 ORDER BY MEASUREGROUP_NAME";
             const string QUERY_FORMATSTRINGS = @"
 SELECT