improve method comments relating to pve builtin return objects,

add paths to create and delete network interfaces,
check for interface existence in modify interface,
add vlan specification to user config and use in network interface creation,
fix disk path security by checking disk existence or nonexistence,
TODO: check create and mount disk against allowed bus types

Signed-off-by: Arthur Lu <learthurgo@gmail.com>

localdb.json.template

@@ -77,6 +77,7 @@
 					"max": 199
 				},
 				"pool": "examplepool",
+				"vlan": "100",
 				"templates": {
 					"lxc": {
 						"net0": {