Add Apache 2.0 license id lines to source files

[jafingerhut]

No description provided.

[jafingerhut]

This is an attempt to add SPDX-License-Identifier lines to all source files that do not have them already, but not to auto-generated source files.

I also add explicit Copyright lines to files that did not have them already. I used the individual who first added the file to this repository as the name to assign the copyright to. Some of you might prefer that the copyright be assigned to the company you were working for at the time. Let me know if there are any added Copyright lines you would prefer to change.

@Dscano @Yi-Tseng @duskmoon314

[chrispsommers]

@jafingerhut thanks for this, let's discuss at the next meeting on Feb 14. Also it needs to be synced to main.

[jafingerhut]

@jafingerhut thanks for this, let's discuss at the next meeting on Feb 14. Also it needs to be synced to main.

Sure, there is no rush on merging this.

[jafingerhut]

Closing this PR, as I think the more up to date PR #545 should be preferred over this one.