+ statistics: store in separate file

+ GET /control/stats handler

home/config.go

@@ -12,6 +12,7 @@ import (
 	"github.com/AdguardTeam/AdGuardHome/dhcpd"
 	"github.com/AdguardTeam/AdGuardHome/dnsfilter"
 	"github.com/AdguardTeam/AdGuardHome/dnsforward"
+	"github.com/AdguardTeam/AdGuardHome/stats"
 	"github.com/AdguardTeam/golibs/file"
 	"github.com/AdguardTeam/golibs/log"
 	yaml "gopkg.in/yaml.v2"
@@ -68,6 +69,7 @@ type configuration struct {
 	controlLock      sync.Mutex
 	transport        *http.Transport
 	client           *http.Client
+	stats            stats.Stats
 
 	// cached version.json to avoid hammering github.io for each page reload
 	versionCheckJSON     []byte