Doc: corrected link/example errors

Update pro files after move gestures folder
Update snippet statements
Corrected path in imagegestures.pro

Task-number: QTBUG-34749

Change-Id: Icc19908914e36507e412ab63bf0cc2809aa48e17
Reviewed-by: Jerome Pasion <jerome.pasion@digia.com>
Update some more screenshots in qtbase/examples/widgets.

The screenshots were taken on Windows 7 with the Aero theme.

Change-Id: I2517664e25389f4fb87408daec7b720dfb785bf0
Reviewed-by: Topi Reiniö <topi.reinio@digia.com>