SSU2: Token improvements and fixes part 1

- Set cache size based on connection limit
- Track average inbound cache eviction time
- Set inbound expiration based on cache time
- Reduce max inbound expiration
- Fix saving inbound token sent after relay response or hole punch
- Dont send or save tokens if we are symmetric natted
- Sort persisted tokens by expiration so they are expired in correct order on reload
- Periodically expire tokens from cache
- Add getters to Token class
- Add missing case IPV4_SNAT_IPV6_UNKNOWN to EnumSets

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

@@ -18,7 +18,7 @@ public class RouterVersion {
     /** deprecated */
     public final static String ID = "Git";
     public final static String VERSION = CoreVersion.VERSION;
-    public final static long BUILD = 3;
+    public final static long BUILD = 4;
 
     /** for example "-test" */
     public final static String EXTRA = "";