Improve thesaurus description according to SKOS thesaurus conceptScheme

[fxp]

Thesaurus header may contain more description which could be added to ISO19139 thesaurus description.

Add support for:

• alternative title (dc:alternative)
• edition (owl:versionInfo)
• thesaurus identifier

if provided.

Example:

    <skos:ConceptScheme rdf:about="http://vocab.nerc.ac.uk/scheme/ICANCOERO/current/">
        <dc:title>International Coastal Atlas Network Coastal Erosion Thesaurus</dc:title>
        <dc:alternative>ICAN Coastal Erosion</dc:alternative>
        <dc:description>Thesaurus containing coastal erosion dataset (including GIS layer) terms
            compiled by ICAN and mapped to a global thesaurus. Includes both markup and discovery
            terms from the mapped components.</dc:description>
        <dc:creator>International Coastal Atlas Network</dc:creator>
        <dc:publisher>Natural Environment Research Council</dc:publisher>
        <dc:date>2011-10-07 02:00:09.0</dc:date>
        <owl:versionInfo>3</owl:versionInfo>