make traceorder a flaglist:
make traceorder a flaglist:

- set dflt to 'grouped' when a legendgroup is present in data
- add isGrouped and isReversed helper functions

iongroup/plotly.js,plotly/plotly.js,aburato/plotly.js,etpinard/plotly.js,etpinard/plotly.js,plotly/plotly.js,asolagmbh/plotly.js,asolagmbh/plotly.js,iongroup/plotly.js,plotly/plotly.js,plotly/plotly.js,aburato/plotly.js,asolagmbh/plotly.js,etpinard/plotly.js,iongroup/plotly.js