for the Slic3r Prusa Edition.
Hopefully a fix of https://github.com/prusa3d/Slic3r/issues/258
by moving the 2D thumbnail generation to the main thread and
forcing the simple 2D convex hull for even the small objects.
if there is any valid option available. This feature has been asked for
by the Prusa3D customers as the '- default -' option has nothing to do
with the actual printer and when selected accidentally, it could even
lead to a printer damage.
made configurable. Now one may hide the "controller" tab and the USB/serial
connection configuration from the preferences. This is useful for someone,
who never connects his printer to the computer by a cable.
