Added xml UI for the avfilter.median

data/effects/avfilter/avfilter_median.xml

+<!DOCTYPE kpartgui>
+<effect tag="avfilter.median" id="avfilter.median">
+	<name>Median</name>
+	<description>Pick median pixel from certain rectangle defined by radius.</description>
+	<author>libavfilter</author>
+	<parameter type="animated" name="av.radius" min="1" max="127" default="1" decimals="3">
+		<name>Spatial sigma</name><comment>Median radius</comment>
+	</parameter>
+	<parameter type="animated" name="av.radiusV" min="0" max="127" default="0" decimals="3">
+		<name>Median vertical radius</name>
+	</parameter>
+	<parameter type="animated" name="av.percentile" min="0" max="1" default="0.5" decimals="3">
+		<name>Median percentile</name>
+	</parameter>
+	<parameter type="list" name="av.planes" default="1" paramlist="0;1;2;3;4;5;6;7;">
+        <paramlistdisplay>Alpha,Y,U,V,Red,Green,Blue,All,</paramlistdisplay>
+                <name>Planes</name>
+        </parameter>
+</effect>