Ensure license files are included and consistent

[stuartcampbell]

Not all license files are included with the installations.

This may be relevant to #374 as well.

[prjemian]

In #374, there was some mention of whether GPL or LGPL. That seems to be the point here.

[prjemian]

• https://www.gnu.org/licenses/gpl-faq.en.html
• https://resources.whitesourcesoftware.com/blog-whitesource/top-10-gpl-license-questions-answered

[prjemian]

@yayahjb suggests we use LGPL throughout. @stuartcampbell - sound OK?