add test mwe file

libmwereader/test_mwe.xml

+<?xml version='1.0' encoding='utf-8'?>
+<units_description tagset='kipi'>
+	<macros>
+		<m>
+			<name>SubstSubstFix</name>
+			<var>S1,S2</var>
+			<con>
+				and(
+					inter(base[0],$s:S1),
+					inter(class[0],{subst,ger,depr}),
+					inter(base[1],$s:S2),
+					inter(class[1],{subst,ger,depr}),
+					inter(cas[0], cas[1])
+				)
+			</con>
+		</m>
+	</macros>
+	<LU>
+		<LUbase>Jan Paweł</LUbase>
+		<t>fix</t>
+		<pat>#SubstGenSubstFix("jan","paweł")</pat>
+		<h>inter(cas[$H], {nom})</h>
+		<class>subst</class>
+	</LU>
+</units_description>
\ No newline at end of file