contentType: Reply back proper contentTypes based on the file extension.

Currently the server would set 'application/octet-stream' for all
objects, set this value based on the file extension transparently.

This is useful in case of minio browser to facilitate displaying
proper icons for the different mime data types.

web-definitions.go

@@ -51,6 +51,8 @@ type ObjectInfo struct {
 	LastModified time.Time `json:"lastModified"`
 	// Size in bytes of the object.
 	Size int64 `json:"size"`
+	// ContentType is mime type of the object.
+	ContentType string `json:"contentType"`
 }
 
 // PutObjectURLArgs - args to generate url for upload access.