Fixes to several deficiencies in the Mdl saving code causing issues with Winquake:
- Onseam flag uses the value 32 instead of 1 to prevent visual corruption
- Added helper functions to correct bbox_max and bbox_min values for frame to prevent a crash in winquake
- added recalculate_header function to calculate correct values for boundingradius and average_size fields, improving rendering in winquake
The helper object has been enhanced to automatically run these helper functions on the mdl file before each save.