Documentation: Clarify etcd security documentation

Signed-off-by: Vincent Ambo <vincent@kivra.com>
*: change all ID to uint64
Merge pull request #1289 from coreos/uint

*: change all ID to uint64
Merge pull request #972 from tazjin/etcd-security-docs

Documentation: Clarify etcd security documentation
raft: protobuf messageType
etcdserver/raft: set context for bootstrap addnode entries
etcdserver: apply bootstrap conf change
Merge pull request #1259 from unihorn/156

etcdserver/raft: apply bootstrap addnode entries
main: fix typos and initial-cluster references
Merge pull request #1295 from jonboulle/typos

main: fix typos and initial-cluster references
Merge pull request #1293 from unihorn/160

raft: protobuf messageType
etcdserver: change machines endpoint to members
Merge pull request #1290 from coreos/member_endpoint

etcdserver: change machines endpoint to members
etcdserver: clean NewServer
etcdserver: add shouldDiscover
etcdserver: add s.apply
etcdserver: Id -> ID
etcdserver: fix typo
Merge pull request #1288 from coreos/cleanup

etcdserver: clean NewServer
etcdhttp: add PUT and DELETE on /v2/admin/members/