[ADD] picking_line_description module v.7.0

Moving the MP: https://code.launchpad.net/~agilebg/stock-logistic-flows/adding_picking_line_description_7/+merge/219800
IMHO, the odoo module `sale_stock` is far from being an exemplary module, it has tonnes of depricated code, it has inconsistent style / none at all. They don't even follow their own community-guidelines and refuse fixes which fix style (stated in contributing wiki page).

`odoo.py scaffold` disregards the guidelines also, but at least, they do the naming right, IMHO.

The reason for which to separate code by model name is simple: to make the life easier for the maintainers of the code.

In the future, if a dev want to edit the code, we'd rather look for the modifications to settings in the file which is named after its own model, so: 

sale.stock modifications are in sale_stock.py, sale_stock_view.xml, sale_stock_data.xml, sale_stock_demo.xml

I think you can agree that it's less of a headache than grepping the whole directory. It's simply good style. This saves maybe a minute, but the minutes add up.

Additionally, the naming allows a dev to know exactly what models are affected without having to peek inside each file. If there's a crash related to the sale.stock model, you can easily tell which modules affect it.