Clarify which repos are active vs legacy or deprecated, and what they do

[marclaporte]

As a follow-up to: #1

[marclaporte]

A start: #3

[iliajie]

A start: #3

Merged, thank you!

[iliajie]

What we should do, I think, is move all Git history from virtualmin-lamp-stack-ubu to virtualmin-lamp-stack-deb. The name -deb would be consistent with the virtualmin-core-deb repo as well.

Alternatively, to keep it simple, we could rename virtualmin-lamp-stack-deb to virtualmin-lamp-stack-deb-archive and then rename virtualmin-lamp-stack-ubu to virtualmin-lamp-stack-deb, which would be much easier.

But it's up to Joe to decide.