StatusBar class calls are commented out and replaced with notifications.
SlicicingProgress notification shows progress of slicing, ProgressIndicator notification handles other progress information, like arrange objects etc.
The following threads are named with this commit:
slic3r_main, slic3r_BackgroundSlicingProcess,
slic3r_tbbpool_xx_yy where xx is a one based index of the TTB thread
and yy is the platform thread ID.
