Mass compile repo to LV 2019

[Karl-G1]

• [x] This contribution adheres to CONTRIBUTING.md.

What does this Pull Request accomplish?

• Update readme with new LabVIEW version
• Mass compile repo and save project for LV 2019
• Change build to target LV 2019 and 2020 only

Why should this Pull Request be merged?

Prepare for 21.0 and 64-bit library support

What testing has been done?

None yet

[Karl-G1]

The build failed while copying FXP libraries. It looks like it may be easier to combine the mass compile with the target support changes for this repo, so I will mock up those changes.

I re-kicked the builds after looking at the directory structures from merging the latest FXP changes into main. It looks like there was a race condition around when it was submitted/finished, and the second build here is working as-is.

Edit: and kicking one more time because 2019 Scripting Examples failed to build, although nothing changed and 2020's passed.