Rename burst to signum

[damccull]

Spent some time renaming every type, method, and variable that included the word 'burst' to include either 'signum' or 'signa', as appropriate, and correctly cased.

I purposely left strings alone for now as that will require more manual intervention that just letting the IDE handle renaming tokens. Strings will require gaining an understanding of the process they're each a part of and ensuring that changing them doesn't break anything.

I also purposely left any javascript, OpenAPI, or GUI webapp code alone, as I do not yet understand how any of those work.

This is mutually exclusive with #787 at the moment, but I will rebase whichever doesn't get approved first and push corrections.

[ohager]

Luckily I recently added the build action on PRs - 292 files is a big change. But LGTM.
Thanks for the effort. I was thinking of doing the same. One tiny thing we might want to improve is the brs package name. But let's do another time.

[damccull]

I was going to do the package name too but wasn't sure what exactly to call it, and I wanted to see how this would merge before attempting the even larger package rename.

How about 'srs'?