[FIX] product: creation of reference uom

Set a default value for factor when creating a new uom.
Could not create a new UoM with type reference (if creates a reference uom, no need to pass a factor).

Change the readonly filter to (type = bigger) to make the field writable for reference uom.
This is needed to force the reset of the factor when switching of type (onchange_type).
As the field was readonly, kept the old value for factor.
[FIX] project_timesheet: date of created analytic line not in user tz

When the user was in timezone UTC + 1, and added a project.task.work which created an analytic entry line (timsheet activity), if the datetime was set to 11/25 00:00:00, the date on the analytic line was set to 11/24, because this was the truncated stored value(UTC Time), which was 11/24 23:00:00
[FIX] account: prevent invoice line duplication on partner duplication

If a company contact (a partner with a company set as parent) had invoices, and the company of this contact was duplicated, all the invoices lines were duplicated,  on the original invoice moreover (new lines were added on existing invoices)