https://github.com/autodesk-forge/
https://sharecad.org/zh/DWGOnlinePlugin
http://3d-viewers.com/license.html
https://sourceforge.net/projects/js-cad/files/?source=navbar
https://github.com/mmik005/js-cad
https://github.com/qcad/qcad
http://duchangyu.github.io/51CTO/#/25
https://github.com/LibreCAD/LibreCAD
http://www.qcad.org/en/component/content/article/78-qcad/111-qcad-compilation-from-sources
https://github.com/Autodesk-Forge/design.automation-custom-data-viewer
DWG to PNG:
https://github.com/loftuxab/alfresco-vector-transformations-module