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