Added new extension "sync"

Periodically poll registries and pull images according to sync's config
Added sync on demand, syncing when clients asks for an image which
zot doesn't have.

Signed-off-by: Petu Eusebiu <peusebiu@cisco.com>

cmd/zot/main_test.go

@@ -4,14 +4,15 @@ import (
 	"testing"
 
 	"github.com/anuvu/zot/pkg/api"
+	"github.com/anuvu/zot/pkg/api/config"
 	"github.com/anuvu/zot/pkg/cli"
 	. "github.com/smartystreets/goconvey/convey"
 )
 
 func TestIntegration(t *testing.T) {
 	Convey("Make a new controller", t, func() {
-		config := api.NewConfig()
-		c := api.NewController(config)
+		conf := config.New()
+		c := api.NewController(conf)
 		So(c, ShouldNotBeNil)
 
 		cl := cli.NewRootCmd()