added safety checks, DXF support, fixes to TIN support
added safety checks, DXF support, fixes to TIN support

markraz/vtp,nakijun/vtp,markraz/vtp,seanisom/vtp,seanisom/vtp,markraz/vtp,markraz/vtp,nakijun/vtp,markraz/vtp,seanisom/vtp,nakijun/vtp,seanisom/vtp,nakijun/vtp,nakijun/vtp,seanisom/vtp