Fix schema location bug

[daleroberts]

When an XML file with data has a hardcoded schema location like:

<?xml version="1.0"?>
<DnaXmlFormat type="Measurement File" referenceframe="GDA2020" epoch="01.01.2020" xmlns:xsi="http://www.w3.org/2001/XMLSchema-instance" xsi:noNamespaceSchemaLocation="C:\DynAdjust\exe\DynaML.xsd">
  <!-- Type D Direction set -->

Fix the problem whereby dnaimport can hang because it can't find that file. Now it checks if it can use DynaML.xsd from the current directory, otherwise fail with an error.