Compute potential quantities for both product templates and variants. To keep the code simple, only the biggest potential of any single variant is accounted for in the template's potential.
Take all levels of phantom BoM into account, respects validity dates etc. thanks to the use of the standard method _bom_explode, as suggested by @gdgellatly in https://github.com/OCA/stock-logistics-warehouse/pull/5#issuecomment-66902191
Improve tests, rewritten in python.
Adhere to new file/manifest/README conventions.
Simplify copyright headers
