Ticket #141 (defect)

Several defects exist with the ContactMetadata parsing:

• PostCode tag was incorrectly searched as Postcode
• Any error in parsing prevented reading in of subsequent tags

This patch re-implements the parser to fix these defects and also includes a check that makes sure that the ContactInformation block is non-empty before attempting to parse it. This last was necessary to make http://openaerialmap.org/wms/ parse correctly. (Formerly it would break because of the dereferencing of .text for the Name tag that was assumed to exist).