DXF blocks are virtual groups of items.
The insert entity is what actually places all the block contents at a given coordinate.
This should fix importing drawings from professional CAD tools like SolidWorks that will have a good bit of blocks.
* Do not compile dxf old files.
* import gfx, gal mode: make absolute placement working.
* Import gfx in legacy canvas: use it and make interactive placement working
* Take imported line width in account. Ensure DXF line thickness is OK.
* handling empty files in legacy mode.