QmlDesigner.Instances: Move instances out of process

QmlDesigner.Instances: Move instances out of process

The complete qml emulation layer (instances) is moved
into another external process (qmlpuppet).

Summary of architectural changes:

- Asynchronous messaging
    Handling commands and data transfer asynchronously reduces the
    amount of context switches between processes.

- Proxy classes for client process
    This classes abstract the inter process communication

- QVariant based command parsing and serialization
    Using LocalSocket in bidirectional manner for communications
    of commands and data transfer.

- Integer based identifier instead of ModelNode in client process
    The qml emulation layer (instances) has no more depencies to our
    internal data model.

- Timer based rendering
    Rendering in instances is controlled by a timer. Only dirty items
    are updated.