[FIX] res_partner: add parent_name related field

In some cases (e.g. with record rules), the name_get might not have access
to the parent name. Therefore a parent_name related field solves the
issue (as it read with as superuser).
[FIX] point_of_sale: no need to specify numeric digits

In the report pos order, average_price was set as a numeric(16,2), therefore, if the amount was too big, it led to a psql crash:
A field with precision 16, scale 2 must round to an absolute value less than 10^14.
[FIX] web: show oe_sidbar text on internet explorer