Create localized strings in the loc directory

[lushc]

Label strings that replace XML element names with different phrases and rollover help strings can be found in the loc/<language_abbreviation>/labels.xml directory, e.g. loc/eng/labels.xml.

Currently only the labels provided are those from the iso19139 plugin detailing iso19139/19115 elements, therefore all gvq/gmd19157/updated19115/un element names are displayed raw (making it not much better than viewing an XML file directly!)

More intelligible/alternative names and tooltip strings should be provided where possible for all elements in the GVQ schemas.