Comments to exlain progress directions. Some categories need to be expanded but do not need to checked for divergence. Checking divergence has a higher management cost. By not checking divergence, we reduce a bit the quality of simulation and at the same time the management costs of data. Use API of SolverTool instead of creating by handle solver processes.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@31326 20353a03-c40f-0410-a6d1-a30d3c3de9de