Add Element 'Label(s)' as CoMPAS SCL Extension to the CoMPAS XSD

[dlabordus]

User Story
Add a CoMPAS Extension to store labels for a SCL File to make filtering easier if a lot of SCL Files are stored in the SCL Data Service.

Additional information
The idea is the add a extra Element 'Labels' to the CoMPAS SCL Extension. This Element will be added to the private section of the SCL Element (beside the SclName and SclFileType)

    <xs:simpleType name="tCompasLabel">
        <xs:annotation>
            <xs:documentation>Label added to the SCL File to filter on</xs:documentation>
        </xs:annotation>
        <xs:restriction base="xs:normalizedString">
            <xs:minLength value="1"/>
            <xs:pattern value="[A-Za-z][0-9A-Za-z_-]*"/>
        </xs:restriction>
    </xs:simpleType>

    <xs:complexType name="tCompasLabels">
        <xs:annotation>
            <xs:documentation>List of Labels belonging to the SCL File to filter on with a maximum number of labels</xs:documentation>
        </xs:annotation>
        <xs:sequence>
            <xs:element name="Label" type="tCompasLabel" minOccurs="0" maxOccurs="20"/>
        </xs:sequence>
    </xs:complexType>

    <xs:element name="Labels" type="tCompasLabels"/>

Example of Private Section in SCL XML File

<SCL xmlns="http://www.iec.ch/61850/2003/SCL" xmlns:compas="https://www.lfenergy.org/compas/extension/v1" 
          release="4" revision="B" version="2007">
  <Private type="compas_scl">
    <compas:SclName>MiniGrid</compas:SclName>
    <compas:SclFileType>CID</compas:SclFileType>
    <compas:Labels>
     <compas:Label>Label1</compas:Label>
     <compas:Label>Label2</compas:Label>
    </compas:Labels>
  </Private>
  ...
</SCL>

[dlabordus]

Maybe also make a little change to the element type 'tCompasSclName', so that the minimal length will be at least 1.

    <!--
    SCL Name element.
    -->
    <xs:simpleType name="tCompasSclName">
        <xs:annotation>
            <xs:documentation>Name of the SCL configuration, extension excluded</xs:documentation>
        </xs:annotation>
        <xs:restriction base="xs:normalizedString">
            <xs:minLength value="1"/>
        </xs:restriction>
    </xs:simpleType>