add QImage support and extend QQuickImageProvider implementation

[svitoos]

• added QImage wrapper
• added the callback data parameter to the provider's create function.
• dos_qquickimageprovider_create replaced by dos_qquickimageprovider_create_qimage/qpixmap
• RequestPixmapCallback replaced by DosRequestPixmapCallback and DosRequestImageCallback

[filcuc]

I dunno if we can break the api maybe we can keep both apis in place and mark the previous one as deprecated

[svitoos]

I restored dos_qquickimageprovider_create and RequestPixmapCallback and marked them as deprecated.