demand moves have the same date it can happen that the supply is
effectively ignored if considered as staring move of the
grouping and there are more groups to be done after it.
A test case include in this fix depicts in detail the
the problem and ensures no regression.
* You can know integrate with different forecasting mechanisms.
As a consequence integration with stock_demand_estimate is moved
to a new module (mrp_multi_level_estimate).
* As agreed by the authors, the module is re-licensed to LGPL-3.
