Add dynamic_study_export_mode property

Author: forus

src/main/java/org/cbioportal/legacy/service/FrontendPropertiesServiceImpl.java

@@ -194,8 +194,8 @@ public enum FrontendProperty {
         enable_study_tags("enable_study_tags", null),
         enable_darwin("enable_darwin", null),
 
-        clickhouse_mode("clickhouse_mode", "false");
-        
+        clickhouse_mode("clickhouse_mode", "false"),
+        dynamic_study_export_mode("dynamic_study_export_mode", "false");
 
 
         private final String propertyName;