Check if an required extrafield is filled.
Method setOptionalsFromPost now return -1 if required field is blank
Do not create invoice if required extrafields are empty
Fix : bad test field when checking extrafield is required
Check required extrafields on proposals
Fix : show input fields if missing required extrafield when editing
invoice
Check required extrafields on orders
Merge pull request #1136 from jfefe/extrarequired

Missing checks on extrafields