[FIX] models: simplify partial setup of fields, let it crash silently

The setup of relational fields may be problematic, as they may refer to unknown
models via custom relational fields.  In a partial setup, do not try to skip
the field setup, but let it go and silently catch any exception if it crashes.
[FIX] crm_lead: don't rewrite user_id. Value has not been updated so it's useless. Some module check that user_id is in vals to trigger others actions for nothing.
[FIX] purchase_requisition: change active_id to tender_id in widget context

this is due to commit 6ed774de614a2977a8d186a14ef2cd45a76e7a2e and a37bad205b13cec4f19f8e84e28801278e3e36ca which removes the active_id from context if the target==curent which is the case of this widget, we therefore can not use active_id here.

fix #2385
[FIX] product_visible_discount: fix display of unit price according to rule base price like in 7.0 as requested by gab
[FIX] config: fix parsing of geoip db paramater, rename command-line option for consistency
Merge branch '8.0' of github.com:odoo/odoo into 8.0