bump version to 6

Author: risicle

build.xml

@@ -9,7 +9,7 @@
          See https://josm.openstreetmap.de/wiki/DevelopersGuide/DevelopingPlugins
     -->
     <property name="plugin.author" value="Robert Scott"/>
-    <property name="plugin.version" value="5"/>
+    <property name="plugin.version" value="6"/>
     <property name="plugin.class" value="org.openstreetmap.josm.plugins.markseen.MarkSeenPlugin"/>
     <property name="plugin.description" value="Marks 'seen' areas of the map"/>
     <property name="plugin.icon" value="images/icons/24x24/markseen.png"/>