[FIX] mail: access link generaTION

Catch only the error related to the access of the linked record.
Previous was hidding error to access the ir.config_parameter and eventual other
errors from the orm.
Uses SUPERUSER_ID to access instance URL (e.g. portal has no access to it).
Fixes #4234 #4234
[FIX]web_gantt: value rendering with decimal separator other than dot
[MERGE] forward port of branch 7.0 up to 60a361c
[FIX] web_gantt: duration in business days if delay not set

delay already being the hours amount in business hours

opw-620189
[MERGE] forward port of branch 7.0 up to f833d2e
[FIX] crm_partner_assign: more precise geolocation

Google api geolocation service returns a precise latitude and longitude, greater or equal than 5 digits
The precision is important as storing 2 digits instead of 5 can lead to an inaccuracy of allmost half a mile.
[FIX] account: prevent selecting company's contacts for manual account.move.line

Only the commercial partner (parent company) should be set in partner field of
an account.move.line.
Fixes #4261, opw 618763
[FIX]stock: return of 'To Be Invoiced' picking should also be invoiced

When creating a return picking, the default invoice state is 'To Be Invoiced' if
returned picking was invoiced. However if the invoice of the picking has not
been generated yet (state '2binvoiced'), the return should also be invoiced.
Fixes #4002
[FIX] account: aged partner balance, advance partial payment

Partners totals were not correct if the partner paid partially an invoice in advance
For an invoice of 20.000 in the future, with a payment made in advance of 5000
The column not due must contains 20.000, as the amount is not yet due
One of the column 1-30, 30-60, ... (accordingly on when the payment was made). must contains -5000
The total should be 15.000
[MERGE] forward port of branch 7.0 up to 43cf6d5
[MERGE] forward port of branch saas-3 up to 36bf774
Merge branch '8.0' of https://github.com/odoo/odoo into 8.0-linux64