20120821

I united the Account and AccountGroup models from lino.modlib.debts and lino.modlib.accounting to a common new module lino.modlib.accounts. Added new Model accounts.Chart.

New fixture lino.modlib.accounts.fixtures.mini is an attempt to create a “universal account chart”

TODO:

• translations

• apps.pcsw.migrate:

  debts_AccountGroup -> accounts.Group debts_Account -> accounts.Account