Add a label field to the project information

The difference between the version number (1.0) and the label (2013.03)
is: The version is time-independent but shows the level of compatibility,
see e.g. <http://www.semver.org>, whereas the label is a marketing tool
which describes the project progress.

dune.module

@@ -1,5 +1,6 @@
 Module: opm-autodiff
 Description: Utilities for automatic differentiation and simulators based on AD
 Version: 0.1
+Label: 2013.03
 Maintainer: atgeirr@sintef.no
 Depends: opm-core