License header in src/ are inconsistent

[ruebot]

Assuming #50 is merged.

The license headers in each of the files in src/main, src/headers, and src/tests are all a little bit different.

Can we pick one, or come up with something new, and apply it to all of them?

[ianmilligan1]

The one in either src/main or src/headers probably makes the most sense to me.

[ruebot]

Sorry, realized I missed a bit of the second sentence, and updated it. Basically what I'm getting at is that they're all a bit different, and we need to normalize them.

[ianmilligan1]

What do you think @greebie?

[greebie]

YES - licenses should be normalized. I think this is an Archives Unleashed project now, so it should apply the same license as AUK an AUT.