7.0 advanced inventory

The modules added here let users handle big and complex stock inventory.
This quite a big contribution, so to ease the review I've split it into 2 commits: 
- 55669fb7060a0cfd19d477221b5cb72743d548aa is about making sure the inventory is reliable even on big installations: purging products not recorded, blocking locations etc.
- 4e6c889806eb54b2a9d346e1ec73c1f2ee574a85 is about splitting big inventories into several smaller ones, to let managers delegate part of the inventory and to get a global view of the progress during the physical counting operations.

Both modules have been implemented in production by at least Numérigrape and Acsone for large and complex inventories.

This pull request supersedes the previous merge proposals made on Launchpad:
- https://code.launchpad.net/~numerigraphe-team/stock-logistic-warehouse/7.0-inventory-location/+merge/223880
- https://code.launchpad.net/~numerigraphe-team/stock-logistic-warehouse/7.0-inventory-hierarchical/+merge/223882
- https://code.launchpad.net/~acsone-openerp/stock-logistic-warehouse/some-fixes-lga/+merge/227680