config: add support for float64
config/etcd: fix configs

This new table is pulled from the etcd codebase rather than the docs...

Added:
 GraphiteHost
 PeerElectionTimeout
 PeerHeartbeatInterval
 PeerKeyFile
 RetryInterval
 SnapshotCount
 StrTrace
 VeryVeryVerbose

Fixed types:
 ClusterActiveSize
 ClusterRemoveDelay
 ClusterSyncInterval
 HTTPReadTimeout
 HTTPWriteTimeout
 MaxResultBuffer
 MaxRetryAttempts
 Snapshot
 Verbose
 VeryVerbose

Renamed:
 Cors

Removed:
 MaxClusterSize
config/flannel: correct - vs _
config/fleet: fix configs

Added EtcdKeyPrefix and fixed the types of EngineReconcileInterval and EtcdRequestTimeout.