Tidying & Selectively forward manifests to peers:

* Do not forward manifests to peers that already know that manifest
* Do not forward historical manifests to peers
* Save/Load ValidatorManifests from a database
* Python test for setting ephmeral keys
* Cleanup manifest interface

src/ripple/overlay/impl/PeerImp.cpp

@@ -655,9 +655,11 @@ PeerImp::doProtocolStart()
     onReadMessage(error_code(), 0);
 
     protocol::TMManifests tm;
+    tm.set_history (true);
 
-    overlay_.manifestCache().for_each_manifest(
-        [&](Manifest const& manifest)
+    overlay_.manifestCache ().for_each_manifest (
+        [&tm](size_t s){tm.mutable_list()->Reserve(s);},
+        [&tm](Manifest const& manifest)
         {
             auto const& s = manifest.serialized;
             auto& tm_e = *tm.add_list();