[FIX] models: stored func fields computation on one2many write

On one2many fields writing in an existing record (not when creating new record), the computed stored fields of the one2many were not re-computed correctly
Computed stored fields were marked as modified only if no_store_function was not set to True in the context. no_store_function is set when writing one2many records on an existing record.
Now, these computed stored fields are marked as to be recomputed, but are recomputed later, at the end of the existing record write
Merge branch '8.0' of github.com:odoo/odoo into 8.0
[FIX] point_of_sale: copy/paste error, super must use the apropriate class
[IMP] Cache bundles in ir.attachments instead of LRU
[IMP] website_quote: handle quote and website descriptions

Add field quote_description on product.template and turn website_description from sale.quote.line into a related.
Overwrite write and create methods to synchronise both fields when setting a product.
website_description on product.template is added by website_sale but there is no dependency relations between these modules so we need to define it in both modules.