Integer fields are not allowed to have options

[deborahvandervegt]

<field name='from_month' label='Maand' datatype='INTEGER' required='false'>
    <options>
        <option label='' value=''/>
        <option label='Januari' value='1'/>
        <option label='Februari' value='2'/>
        <option label='Maart' value='3'/>
        <option label='April' value='4'/>
        <option label='Mei' value='5'/>
        <option label='Juni' value='6'/>
        <option label='Juli' value='7'/>
        <option label='Augustus' value='8'/>
        <option label='September' value='9'/>
        <option label='Oktober' value='10'/>
        <option label='November' value='11'/>
        <option label='December' value='12'/>
   </options>
</field>