Added a generic Balance Sheet report based on the content of financial_section category set on Accounts.
To make it work correctly, some categories must have some special IDs. Look at the code for details.

git-svn-id: https://svn.erp5.org/repos/public/erp5/trunk@14762 20353a03-c40f-0410-a6d1-a30d3c3de9de