SusiMail: Don't store attachments of composed email in-memory,

encode them on-the fly (ticket #1668)
- Fix bug corrupting sent text and text attachments
  larger than about 1000 chars (output line length was not limited)
- Fix bug corrupting some sent text and text attachments
  containing '.'
- Fix handling of unimplemented encoders
- Error message improvements
- Add test code for encoders

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 = 12;
+    public final static long BUILD = 13;
 
     /** for example "-test" */
     public final static String EXTRA = "";