PLT-4357 adding performance monitoring (#4622)

* WIP

* WIP

* Adding metrics collection

* updating vendor packages

* Adding metrics to config

* Adding admin console page for perf monitoring

* Updating glide

* switching to tylerb/graceful

vendor/github.com/prometheus/procfs/fixtures/net/ip_vs

@@ -0,0 +1,14 @@
+IP Virtual Server version 1.2.1 (size=4096)
+Prot LocalAddress:Port Scheduler Flags
+  -> RemoteAddress:Port Forward Weight ActiveConn InActConn
+TCP  C0A80016:0CEA wlc  
+  -> C0A85216:0CEA      Tunnel  100    248        2         
+  -> C0A85318:0CEA      Tunnel  100    248        2         
+  -> C0A85315:0CEA      Tunnel  100    248        1         
+TCP  C0A80039:0CEA wlc  
+  -> C0A85416:0CEA      Tunnel  0      0          0         
+  -> C0A85215:0CEA      Tunnel  100    1499       0         
+  -> C0A83215:0CEA      Tunnel  100    1498       0         
+TCP  C0A80037:0CEA wlc  
+  -> C0A8321A:0CEA      Tunnel  0      0          0         
+  -> C0A83120:0CEA      Tunnel  100    0          0         

vendor/github.com/prometheus/procfs/fixtures/net/ip_vs_stats

@@ -0,0 +1,6 @@
+   Total Incoming Outgoing         Incoming         Outgoing
+   Conns  Packets  Packets            Bytes            Bytes
+ 16AA370 E33656E5        0     51D8C8883AB3                0
+
+ Conns/s   Pkts/s   Pkts/s          Bytes/s          Bytes/s
+       4    1FB3C        0          1282A8F                0