directory structure change to work with glide

glide has its own requirements. My previous workaround caused me some
code checkin errors. Need to fix this.

weed/topology/rack.go

@@ -0,0 +1,65 @@
+package topology
+
+import (
+	"strconv"
+	"time"
+)
+
+type Rack struct {
+	NodeImpl
+}
+
+func NewRack(id string) *Rack {
+	r := &Rack{}
+	r.id = NodeId(id)
+	r.nodeType = "Rack"
+	r.children = make(map[NodeId]Node)
+	r.NodeImpl.value = r
+	return r
+}
+
+func (r *Rack) FindDataNode(ip string, port int) *DataNode {
+	for _, c := range r.Children() {
+		dn := c.(*DataNode)
+		if dn.MatchLocation(ip, port) {
+			return dn
+		}
+	}
+	return nil
+}
+func (r *Rack) GetOrCreateDataNode(ip string, port int, publicUrl string, maxVolumeCount int) *DataNode {
+	for _, c := range r.Children() {
+		dn := c.(*DataNode)
+		if dn.MatchLocation(ip, port) {
+			dn.LastSeen = time.Now().Unix()
+			if dn.Dead {
+				dn.Dead = false
+				r.GetTopology().chanRecoveredDataNodes <- dn
+				dn.UpAdjustMaxVolumeCountDelta(maxVolumeCount - dn.maxVolumeCount)
+			}
+			return dn
+		}
+	}
+	dn := NewDataNode(ip + ":" + strconv.Itoa(port))
+	dn.Ip = ip
+	dn.Port = port
+	dn.PublicUrl = publicUrl
+	dn.maxVolumeCount = maxVolumeCount
+	dn.LastSeen = time.Now().Unix()
+	r.LinkChildNode(dn)
+	return dn
+}
+
+func (r *Rack) ToMap() interface{} {
+	m := make(map[string]interface{})
+	m["Id"] = r.Id()
+	m["Max"] = r.GetMaxVolumeCount()
+	m["Free"] = r.FreeSpace()
+	var dns []interface{}
+	for _, c := range r.Children() {
+		dn := c.(*DataNode)
+		dns = append(dns, dn.ToMap())
+	}
+	m["DataNodes"] = dns
+	return m
+}