Graphs: Clean up font setting, fix bugs (ticket #2684)

Unit font now monospaced on Linux and Mac as intended
Don't set Droid Sans font, not present in any platform by default
Fix font scaling for Japanese
Detect more RTL languages
Make fonts configurable

router/java/src/net/i2p/router/RouterVersion.java

@@ -18,7 +18,7 @@ public class RouterVersion {
     /** deprecated */
     public final static String ID = "Monotone";
     public final static String VERSION = CoreVersion.VERSION;
-    public final static long BUILD = 5;
+    public final static long BUILD = 6;
 
     /** for example "-test" */
     public final static String EXTRA = "";