Tunnels: Fix build request Bloom filter (ticket #1746)

Change from 60s DHS to 60m DBF
Use reply key as filter key, not first part of
encrypted data, to match the specs and hopefully reduce dups
BuildMessageProcessor cleanups
log and stat tweaks
remove deprecated methods
remove some timing measurements
javadocs

core/java/src/net/i2p/data/SessionKey.java

@@ -11,7 +11,9 @@ package net.i2p.data;
 
 /**
  * Defines the SessionKey as defined by the I2P data structure spec.
- * A session key is 32byte Integer. 
+ * A session key is a 32 byte Integer. 
+ *
+ * To create one with random data, use I2PAppContext.keyGenerator().generateSessionKey().
  *
  * @author jrandom
  */
@@ -19,6 +21,7 @@ public class SessionKey extends SimpleDataStructure {
     private Object _preparedKey;
 
     public final static int KEYSIZE_BYTES = 32;
+    /** A key with all zeroes in the data */
     public static final SessionKey INVALID_KEY = new SessionKey(new byte[KEYSIZE_BYTES]);
 
     public SessionKey() {