make hybrid db optional

@@ -116,7 +116,7 @@ public class ThingsboardInstallService {
 
                 log.info("Installing DataBase schema...");
 
-                databaseSchemaService.createDatabaseSchema();//TODO
+                databaseSchemaService.createDatabaseSchema();//TODO issue 1005 - create both SQL and C* schemas in hybrid mode
 
                 log.info("Loading system data...");
 

@@ -164,7 +164,8 @@ database:
   entities:
     type: "${DATABASE_TYPE:sql}" # cassandra OR sql
   ts:
-    type: "${DATABASE_TYPE:cassandra}" # cassandra OR sql
+    type: "${DATABASE_TYPE:sql}" # cassandra OR sql (for hybrid mode, only this value should be cassandra)
+
 
 # Cassandra driver configuration parameters
 cassandra: