Add after keyword argument to insertcols!

[CameronBieganek]

Currently you have to do this if you want to insert columns after a certain column:

df = DataFrame(a=1:2, b=3:4, c=5:6)
i = findfirst(==(:b), propertynames(df))
insertcols!(df, i+1, :x => 7:8)

It would be nice if there were a boolean keyword argument after which defaults to false.

[bkamins]

Note that you can just write columnindex(df, :b) + 1. Other than that it could be added in the future.

[pdeffebach]

Re-ordering data more broadly is something Stata does really well. An after keyword is used heavily there.