return `scaleSet$scales` as a `data.frame`

[gegnew]

It's annoying to have scaleSet$scales return a single-length nested list (see below); it would be better to return as a dataframe. This is a breaking change.

> scaleSet$scales
[[1]] # <- this is a pain
    channelName   scale.type scale.minimum scale.maximum scale.cofactor
1         FSC-A     LogScale             1        100000             NA
2         FSC-W  LinearScale             1        262144             NA
3         SSC-A ArcSinhScale          -200        262144            150
4       Ax488-A ArcSinhScale          -200        262144            150

[gegnew]

An initial investigation reveals that this may not be possible in any sort of consistent fashion.

This works:

x = jsonlite::fromJSON(content)
y = list()
y$scales = x$scales[[1]]

but none of these do:

x = jsonlite::fromJSON(content)
x$scales = x$scales[[1]]
x$foo = x$xcales[[1]]

z = x$scales[[1]]
x$scales <- NULL
x$scales <- z

x$foo <- z

relevant discussion: rstudio/plumber#69

[gegnew]

I personally find it incredibly annoying to have to to x$scales[[1]] every time I want to access the scales, but maybe happy R users don't feel so strongly about it.