Clean field and domain. Fixing operator (begin). Fix doxyfile.

HySoP/DoxyConf/parmes.doxyfile

HySoP/hysop/domain/box.py

HySoP/hysop/domain/discrete.py

HySoP/hysop/domain/domain.py

HySoP/hysop/domain/grid.py

HySoP/hysop/fields/analytical.py

HySoP/hysop/fields/continuous.py

HySoP/hysop/fields/discrete.py

HySoP/hysop/fields/topology.py

HySoP/hysop/operator/Advection.py

HySoP/hysop/operator/__init__.py

HySoP/hysop/operator/advection_d.py

HySoP/hysop/operator/continuous.py

HySoP/hysop/operator/discrete.py