Incrementing version to 0.2.0.

Adding ``CHANGES.txt`` file. Updating version in top-level
``CMakeLists.txt`` file. Removing old ``VERSION`` and spec files.
Adding ``dpp_msbayes_config.h.in`` template file to create a header with
the package version for use by code.
Merge branch 'release-0.2' into dev

Merging update of version number from release branch.