add stub for mol documentation

git-svn-id: https://dng.biozentrum.unibas.ch/svn/openstructure/trunk@2040 5a81b35b-ba03-0410-adc8-b2c5c5119f08

modules/mol/base/doc/mol.rst

+:mod:`mol` -- Molecular structures and surfaces
+================================================================================
+
+.. module:: mol
+   :synopsis: Contains classes and functions to deal with molecular structures
+              and surfaces
+
+The mol module implement data structure to work with molecular datasets. At its heart lie the :class:`EntityHandle` and :class:`EntityView` classes which represent molecular structures such as proteins, DNA, RNA and small molecules. There are also classes to deal with molecular surfaces.
+
+.. toctree::
+  
+  entity
+  editors
+  query
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