Cleanup and add sanity check for coordinate handling from CSW

[ZakarFin]

So we don't get OutOfMemoryError for very large numbers and we don't need to catch exceptions for missing values.

For example:

Missing values:

    <gmd:geographicElement>
        <gmd:EX_GeographicBoundingBox>
            <gmd:westBoundLongitude>
                <gco:Decimal />
            </gmd:westBoundLongitude>
            <gmd:eastBoundLongitude>
                <gco:Decimal />
            </gmd:eastBoundLongitude>
            <gmd:southBoundLatitude>
                <gco:Decimal />
            </gmd:southBoundLatitude>
            <gmd:northBoundLatitude>
                <gco:Decimal />
            </gmd:northBoundLatitude>
        </gmd:EX_GeographicBoundingBox>
    </gmd:geographicElement>

These will make interpolated WKT throw OutOfMemoryError:

     <gmd:geographicElement>
         <gmd:EX_GeographicBoundingBox>
             <gmd:westBoundLongitude>
                <gco:Decimal>-340282346638529000000000000000000000000</gco:Decimal>
             </gmd:westBoundLongitude>
             <gmd:eastBoundLongitude>
                <gco:Decimal>340282346638529000000000000000000000000</gco:Decimal>
             </gmd:eastBoundLongitude>
             <gmd:southBoundLatitude>
                <gco:Decimal>-340282346638529000000000000000000000000</gco:Decimal>
             </gmd:southBoundLatitude>
             <gmd:northBoundLatitude>
                <gco:Decimal>340282346638529000000000000000000000000</gco:Decimal>
             </gmd:northBoundLatitude>
         </gmd:EX_GeographicBoundingBox>
     </gmd:geographicElement>