PieArcSeries should not have a Doughnut property

[pfried]

I'm submitting a...

[ ] Regression (a behavior that used to work and stopped working in a new release)
[ ] Bug report  
[ ] Performance issue
[ ] Feature request
[ ] Documentation issue or request
[x] Other... Please describe:

Current behavior

The PieArcSeries has a Doughnut property which affects how the pie chart is rendered

Expected behavior

This does not really make sense, either you implicitly set the arcWidth or innerRadius or you will pass explicitly a DonutArcSeries which has the properties

What is the motivation / use case for changing the behavior?

imho it is just bad api design

Environment

Libs:
- react version: X.Y.Z
- reaviz version: X.Y.Z


Browser:
- [ ] Chrome (desktop) version XX
- [ ] Chrome (Android) version XX
- [ ] Chrome (iOS) version XX
- [ ] Firefox version XX
- [ ] Safari (desktop) version XX
- [ ] Safari (iOS) version XX
- [ ] IE version XX
- [ ] Edge version XX
 
For Tooling issues:
- Node version: XX  
- Platform:  

Others:

[amcdnl]

I get it - its more of a shortcut for users who don't understand that. To be frank, I'm not sure I would have figured that w/o reading docs and I'm the author of the lib.