Use OptProp aliases instead of direct property access

Like this we don't have to remember which property is a "normal" property
and which is an object where we need to access it's value property.
Also apparently nested property lookup might have some cost while the
alias seems to be a direct reference and thus probably faster, which
might be important if the property is queried very often (tile debug texts for example).
Reenable Python backend for Qt 5 GUI log

Looks like it has been disabled by mistake during the
asynchronous startup work. :)
Add screen blanking control support to Sailfish OS

The Qt 5 GUI on Sailfish OS can now keep the screen on as long
as needed! :) The screen blanking prevention is bound to modRana
being the currently active application, so it does not keep
the screen on if it is in background or another application is active.

And of course the possibility of the import failing is taken into account
and screen blanking control is automatically disable outside of Sailfish OS.