Expose MaxScript UI Controls to Python as PySide2 Widgets

[bdfbrown]

While there are a lot of redundant widgets (pushButton, checkBox, etc...) there are also several Max specific UI Controls that are not part of PySide2.  There is no equivalent for Rollouts, colorpicker, pickbutton, mapbutton, materialbutton, or curvecontrol.  I made my own rollout widget by modifying the paint event on a custom widget, but it doesn't replicate all behaviors of native Max rollouts (Specifically the ability to drag the widget to re-order the layout) and I am not even sure where to begin with the others.  

Missing Drag handles and would probably break if the UI color scheme was changed.

Having native widgets or a more professionally made equivalent would be great.  Using PySide2 has allowed me to create really detailed and functional UIs, and it would be even better if there was some further integration with Max.