Disambiguated the string "Luminance" for Luminance Effect Name.

data/effects/frei0r_luminance.xml

 <!DOCTYPE kpartgui>
 <effect tag="frei0r.luminance" id="frei0r.luminance" type="video" unique="1">
-	<name>Luminance</name>
+	<name context="Luminance Effect Name">Luminance</name>
 	<description>Creates a luminance map of the image</description>
 	<author>Richard Spindler</author>
 </effect>