Implementing ACS and multiple viewers

[mpsecondacc]

Hi, it would be a good idea to implement WCS and UCS (and ways to manipulate) as this would allow to implement more custom tools later down the road.

Multiple viewers would also be much appreciated :)

[xiangechen]

The work plane should be a concept similar to UCS, though currently there is no prominent prompt when the work plane is changed. The multi-view plan will include options for single, dual, triple, and four viewports, similar to AutoCAD.

[marcosengele]

Multiple views would be amazing!