Build and test failures with Qt 5.6 and Qt 5.3

[Ivan Čukić]

>> - [5.3] kactivities: won't build due to QQuickWidget::setClearColor which
>> is 5.4+ only.
>
> Ivan, can this be worked around?

I'll have to check. (if nothing else, I'll disable that part - it is
for the settings module, not really a part of the framework)

For how long are we going to support 5.3?

Cheers,
Ivan