VOL-1247 : Modified change tuple to include previous and latest data

VOL-1214 : Fixed logs to use the proper mechanism

- Added missing license
- Moved one change tuple statement which would not include proper info

Change-Id: I5a02f6fe92c8b193642294d62f4413ac6edc0c62
diff --git a/db/model/proxy.go b/db/model/proxy.go
index 1939596..0f5ddc7 100644
--- a/db/model/proxy.go
+++ b/db/model/proxy.go
@@ -73,7 +73,7 @@
 
 func (p *Proxy) Update(path string, data interface{}, strict bool, txid string) interface{} {
 	if !strings.HasPrefix(path, "/") {
-		fmt.Errorf("invalid path: %s", path)
+		log.Errorf("invalid path: %s", path)
 		return nil
 	}
 	var fullPath string
@@ -87,7 +87,7 @@
 
 func (p *Proxy) Add(path string, data interface{}, txid string) interface{} {
 	if !strings.HasPrefix(path, "/") {
-		fmt.Errorf("invalid path: %s", path)
+		log.Errorf("invalid path: %s", path)
 		return nil
 	}
 	var fullPath string
@@ -101,7 +101,7 @@
 
 func (p *Proxy) Remove(path string, txid string) interface{} {
 	if !strings.HasPrefix(path, "/") {
-		fmt.Errorf("invalid path: %s", path)
+		log.Errorf("invalid path: %s", path)
 		return nil
 	}
 	var fullPath string