Creating namespace module

The code that creates the 19115-3 namespaces was moved into a file
named create19115-3Namespaces.xsl so that it could be imported into
multiple stylesheets.
Merge pull request #41 from ISO-TC211/renameNamespaceTemplate

This was tested with MD_MetadataPaths.xml and MI_MetadataPaths.xml. The unnecessary namespace declarations no longer exist,