Add NODE_BLOOM service bit and bump protocol version

Lets nodes advertise that they offer bloom filter support explicitly.
The protocol version bump allows SPV nodes to assume that NODE_BLOOM is
set if NODE_NETWORK is set for pre-70011 nodes.

Also adds an option to turn bloom filter support off for nodes which
advertise a version number >= 70011. Nodes attempting to use bloom
filters on such protocol versions are banned, and a later upgade
should drop nodes of an older version which attempt to use bloom
filters.

Much code stolen from Peter Todd.

Implements BIP 111

src/init.cpp

@@ -918,6 +918,9 @@ bool AppInit2(boost::thread_group& threadGroup, CScheduler& scheduler)
     // Option to startup with mocktime set (used for regression testing):
     SetMockTime(GetArg("-mocktime", 0)); // SetMockTime(0) is a no-op
 
+    if (GetBoolArg("-peerbloomfilters", true))
+        nLocalServices |= NODE_BLOOM;
+
     // ********************************************************* Step 4: application initialization: dir lock, daemonize, pidfile, debug log
 
     // Initialize elliptic curve code