Overwrite translation on module update if option is set

Launchpad bug: https://bugs.launchpad.net/ocb-server/+bug/1319285
[FIX] hr_timesheet_sheet: accept custom fields in timesheets

When creating hr.analytic.timesheet do not filter the list of fields to accept but set the list of fields to remove.
Merge pull request #673 from guewen/lp-1319285-translation-overwrite-module-update

[FIX] loading: overwrite translation on module update if option --i18n-overwrite is set