Separated the Marlin G-code flavor from the RepRap G-code flavor

due to the differences in the M203 code
(RepRap firmware has it in mm/min, Marlin in mm/sec).
This difference is important to the G-code time estimator.

Changed the g-code flavor to Marlin for all Prusa3D bundled profiles.

xs/src/libslic3r/GCode.cpp

@@ -400,6 +400,7 @@ void GCode::_do_export(Print &print, FILE *file)
 
     // resets time estimator
     m_time_estimator.reset();
+    m_time_estimator.set_dialect(print.config.gcode_flavor);
 
     // How many times will be change_layer() called?
     // change_layer() in turn increments the progress bar status.