use default freepie UDP port
wiki update
switch back to volatile bool for tracker flags

UI thread is the only writer for the flags. Makes no sense to use more
than volatile.
emit "saving()" after bundle's been updated
allow tying option to tab widget's index
pt: use settings framework

Issue: #96

Model values are recomputed every frame. This shouldn't matter, as
there's very little to compute.

With this change, sliders and other options are applied immediately, and
the "Apply" button is gone.