Note re: Slickgrid version

[fedarko]

While talking with @charles-cowart I realized that I wasn't actually sure which version of SlickGrid was in use (since the "main" SlickGrid repo stopped development almost 3.5 years ago).

After examining our slick.grid.js file, as well as this comment from Amanda, I'm pretty sure we're using the 6pac community fork (which is still actively maintained).

@charles-cowart suggested I make this issue in order to:

1. just make note of this somewhere, because otherwise the next batch of LabControl developers will have to look this up
2. make a note for the future about updating SlickGrid to the newest available version (it looks like the 6pac fork is on v2.4 and we're on v2.3, so if desired we can update to that as a part of this sprint).

[fedarko]

More notes for the future:

• attempting to update SlickGrid (i.e. all of the slick.*.js files we rely on, plus the corresponding plugins) to v2.4.3 straight-up breaks the whole "edit mode" functionality entirely.
• attempting to update just the slick.cellexternalcopymanager.js file to the latest version—and keeping the other SlickGrid JS files as is—doesn't resolve the problem with no autocomplete on pasting detailed in #354. (This is more incentive for addressing #354 via the "checkbox" solution detailed in #464.)

[fedarko]

Another note:

From what I can tell, we currently use an additional grid to simulate a "frozen column" (i.e. keeping the first column in place even when the plate is scrolled horizontally). This is documented in this comment.

It looks like (as of December 2018) SlickGrid officially supports frozen columns, so we could theoretically do away with this hack if we upgrade our SlickGrid version.

[charles-cowart]

I'd like to do away with the additional grid eventually; I will flag this for post full-release TODOs.