@iso-date attributes have no description of their own

[nosvalds]

Is your feature request related to a problem? Please describe.
Applications that programmatically use the IATI-Schema will find no description in <xsd:documentation> for @iso-date attributes. An example of this was Datastore Search (Trello). This seems to be the only attribute where this is the case.

Describe the solution you'd like
Ideally we'd also have a simple description in the @iso-date attributes. See how @type is done below.

Describe alternatives you've considered
For now we will probably use the description of the parent element e.g. <activity-date>, however that could be somewhat confusing because that element also describes other attributes like the @type

  <xsd:element name="activity-date">
    <xsd:annotation>
      <xsd:documentation xml:lang="en">
        The planned and actual start and completion dates of the
        activity. Start dates may reflect either the commencement of
        funding, planning or physical activity. End dates should,
        wherever possible, reflect the ending of physical activity.


        The narrative content may contain text (e.g. 2011Q1) for
        accurately recording less specific dates such as month,
        quarter, or year.
      </xsd:documentation>
    </xsd:annotation>
    <xsd:complexType>
      <xsd:sequence>
        <xsd:element ref="narrative" minOccurs="0" maxOccurs="unbounded" />
        <xsd:any namespace="##other" processContents="lax" minOccurs="0" maxOccurs="unbounded"/>
      </xsd:sequence>
      <xsd:attribute name="type" use="required" type="xsd:string">
        <xsd:annotation>
          <xsd:documentation xml:lang="en">
            An IATI code defining the type of activity date being reported.
          </xsd:documentation>
        </xsd:annotation>
      </xsd:attribute>
      <xsd:attribute name="iso-date" type="xsd:date" use="required"/>
      <xsd:anyAttribute processContents="lax" namespace="##other"/>
    </xsd:complexType>
  </xsd:element>

[andylolz]

I think this is a duplicate of #331.

#331 (comment) points to some explanation of why these descriptions were removed.