Added "known" as a valid model file type
   => 'Known files (*.stl, *.obj, *.amf)|*.stl;*.STL;*.obj;*.OBJ;*.amf;*.AMF;*.xml;*.XML',

When dialog pops up, it can see ALL known file types instead of only stl.
Respect perimeter/infill order when multiple extruders are configured but only one is used
Allow drag and drop for OBJ files
Fix memory leak in avoid_crossing_perimeters. #1044
Merge pull request #1059 from cakeller98/Universal_File_Visibility

Added "known" as a valid model file type
Lower 0.5*w to 0.4*w to fill finer gaps. #1057
Merge branch 'master' into internal-support
Remove scale from G-code comments