add script to dump complete JSON specification for all Bokeh models (#6334)
add script to dump complete JSON specification for all Bokeh models (#6334)

* add script to dump complete JSON specification for all Bokeh models

* script improvements

mindriot101/bokeh,dennisobrien/bokeh,aavanian/bokeh,rs2/bokeh,rs2/bokeh,bokeh/bokeh,philippjfr/bokeh,stonebig/bokeh,DuCorey/bokeh,bokeh/bokeh,mindriot101/bokeh,timsnyder/bokeh,timsnyder/bokeh,dennisobrien/bokeh,dennisobrien/bokeh,DuCorey/bokeh,rs2/bokeh,ericmjl/bokeh,jakirkham/bokeh,aavanian/bokeh,stonebig/bokeh,Karel-van-de-Plassche/bokeh,stonebig/bokeh,rs2/bokeh,DuCorey/bokeh,timsnyder/bokeh,Karel-van-de-Plassche/bokeh,aavanian/bokeh,stonebig/bokeh,DuCorey/bokeh,ericmjl/bokeh,bokeh/bokeh,jakirkham/bokeh,jakirkham/bokeh,jakirkham/bokeh,mindriot101/bokeh,Karel-van-de-Plassche/bokeh,rs2/bokeh,Karel-van-de-Plassche/bokeh,aavanian/bokeh,DuCorey/bokeh,Karel-van-de-Plassche/bokeh,jakirkham/bokeh,philippjfr/bokeh,timsnyder/bokeh,bokeh/bokeh,philippjfr/bokeh,ericmjl/bokeh,dennisobrien/bokeh,timsnyder/bokeh,philippjfr/bokeh,aavanian/bokeh,dennisobrien/bokeh,ericmjl/bokeh,bokeh/bokeh,mindriot101/bokeh,ericmjl/bokeh,philippjfr/bokeh