Fix loading 2x images in Rich Text Documents

There are some issues preventing 2x images from loading, mainly incorrect
testing for exist() by passing an url, which always reports ‘false’.

Task-number: QTBUG-36383
Change-Id: I1e8e5a91b01f1a4ddd3559c2e860db5bc41908ce
Reviewed-by: Morten Johan Sørvig <morten.sorvig@digia.com>
Make QtBearer networkmanager backend respond to wired cabling changes

Cabling changes can be detected right away, so we should act on that
and change the configuration state.

Change-Id: Ifa9709077215567001e11ab655208a2c1b090073
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>
make qtbearer networkmanager defaultConfiguration more reliable

The defaultConfiguration could switch and be either active connection,
so we determine the default should be what has the default route.

Change-Id: I194f27b60e7a3598eca2ff09c2225ba1a46564d9
Reviewed-by: Alex Blasche <alexander.blasche@theqtcompany.com>
WinRT: Add missing manifest specifier for rotation

Add WINRT_MANIFEST.rotation_preference as description which orientation
is allowed or preferred by the app. Valid values for Windows Phone are
portrait, landscape, landscapeFlipped. WinRT also allows portraitFlipped

Task-number: QTBUG-40830
Change-Id: I6b11afcdb72c2c158dadddafc5d90c1d18ab9d8b
Reviewed-by: Andrew Knight <andrew.knight@theqtcompany.com>
Fix crash in QNetworkSession when engine is not set

Task-number: QTBUG-42427
Change-Id: Ie35d5e0f72be3a16ecb6b928e12bc50d9f183590
Reviewed-by: Andy Shaw <andy.shaw@digia.com>
QGraphicsItem: clarify the documentation about caching modes and update()

It is possible that Qt calls paint() several times for an item that
has caching enabled, even without any explicit call to update(). There
are various reasons why that is possible (memory pressure, item gets
transformed, etc.); the important part is that

1) the user must not rely into "caching enabled" = "1 paint() call"
2) the user must always draw the same content from within paint(),
unless update() was called before that call to paint().

Task-number: QTBUG-18410
Change-Id: I2c8d77e6e11aaceffc9a21003dd3f4cc46edd582
Reviewed-by: Venugopal Shivashankar <venugopal.shivashankar@digia.com>
Reviewed-by: Andy Shaw <andy.shaw@digia.com>