update example, add an example pod for portmapping

examples/port-mapping.pod

```
{
        "id": "port-mapping-test",
        "containers" : [{
            "name": "pmtest",
            "image": "busybox:latest",
			"command": ["/bin/nc", "-l", "-p", "1300"]
        }],
        "resource": {
            "vcpu": 1,
            "memory": 128
        },
        "portmappings": [{
			"containerport": "1300-1310",
			"hostport": "3000-3010",
			"protocol": "tcp"
		}]
}
```

Signed-off-by: Wang Xu <[email protected]>

Author: gnawux

examples/file-mapping.pod

@@ -17,7 +17,7 @@
         "volumes": [{
             "name": "resolv.conf",
             "source": "/etc/resolv.conf",
-            "driver": "vfs"
+            "format": "vfs"
         }],
         "tty": true
 }

examples/port-mapping.pod

@@ -0,0 +1,18 @@
+{
+        "id": "port-mapping-test",
+        "containers" : [{
+            "name": "pmtest",
+            "image": "busybox:latest",
+			"command": ["/bin/nc", "-l", "-p", "1300"]
+        }],
+        "resource": {
+            "vcpu": 1,
+            "memory": 128
+        },
+        "portmappings": [{
+			"containerport": "1300-1310",
+			"hostport": "3000-3010",
+			"protocol": "tcp"
+		}]
+}
+

examples/with-volume.pod

@@ -36,11 +36,11 @@
 	"volumes": [{
             "name": "log",
             "source": "",
-            "driver": ""
+            "format": ""
 	},{
             "name": "tmp",
             "source": "/tmp",
-            "driver": "vfs"
+            "format": "vfs"
 	}],
 	"tty": true
 }