Convert the localstorage plugin to v4

Change-Id: I397c3a7e67a65696bb7cb35502e59b49f3928a05
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>
Remove last v8 dependency in qqmlvmemetaobject

Change-Id: If3b45ea3048f6167a121011191aa5f42b2fe2e88
Reviewed-by: Simon Hausmann <simon.hausmann@digia.com>