License header update

docs/license_header.txt

    DBeaver - Universal Database Manager
-   Copyright (C) 2010-2019 Serge Rider (serge@jkiss.org)
+   Copyright (C) 2010-2019 DBeaver Corp and others
 
    Licensed under the Apache License, Version 2.0 (the "License");
    you may not use this file except in compliance with the License.
@@ -12,3 +12,6 @@
    WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
    See the License for the specific language governing permissions and
    limitations under the License.
+
+   Contributors:
+      Serge Rider - initial API and implementation