LICENSE is missing from git repository root directories

As discussed on IRC today:

10:57 < cthiel> good day, would it be possible to put a LICENSE into github.com/xwiki/* repositories, to
refelect what's in http://www.xwiki.org/xwiki/bin/view/Main/License?
11:14 <+tmortagne> cthiel: license is embedded at build time in pretty much everything but indeed it might be
cleaner to also put it at the root of each repository
11:14 <+tmortagne> (right now it's in
https://github.com/xwiki/xwiki-commons/blob/master/xwiki-commons-tools/xwiki-commons-tool-license-resources/src/main/resources/META-INF/LICENSE.vm)
11:15 <+tmortagne> would be great if you could create an issue on jira.xwiki.org so that we don't forget, I
won't have time to take care of that today probably

Thanks in advance!