[FIX] core: correct cron thread registry iteration

Fixes #3387
[FIX] website_sale: don't display twice some products

In list view, the 10 last products of a page were the 10 first products of the next page.
Fixes #3373
[FIX] report: fix report HTML editor scrollbar in Firefox
[FIX] purchase: fixed product_uom and price_unit update on product_id change on purchase.order_line form view
[FIX] fields: make field.store=False on old-style function fields

Clarify the semantics of field attributes:
 - field.store is True when the field is actually stored in the database;
 - field.column is the column corresponding to field or None.

The various field definitions correspond to:
 - new-style stored field: field.store and field.column
 - new-style non-stored field: not field.store and not field.column
 - old-style regular field: field.store and field.column
 - old-style function field: not field.store and field.column
[FIX] account: domain on wrong field

The store recomputation method failed as the search was made comparing id of account.move.line to the account.journal values. Search was returing no result most of the time (opw 615554)
Fixes #2454
[FIX] packaging: debian: set /var/lib/odoo as odoo user home dir