Add support for virtual host redirection

[propheth]

Added the REDIRECT environment variable to solve issues #180, #960, #958, #444, #1095 and an alternative to #1369.
Should work for both HTTP and HTTPS, depending on what is configured and perform a single redirect.

The config below does non-www to www,

environment:
    - VIRTUAL_HOST: test.com,www.test.com,a.test.com
    - REDIRECT: www.test.com
    - LETSENCRYPT_HOST: test.com,www.test.com,a.test.com

will create the 301 redirects below

test.com -> www.test.com
a.test.com -> www.test.com

The config below does www to non-www,

environment:
    - VIRTUAL_HOST: test.com,www.test.com,a.test.com
    - REDIRECT: test.com
    - LETSENCRYPT_HOST: test.com,www.test.com,a.test.com

will create the 301 redirects below

www.test.com -> test.com
a.test.com -> test.com

[alekna]

How about:

• making redirect code configurable
• if not configured, making HTTP/302 a default redirect code

[coaperator]

When is the merger of this PR, #1836 and #1927 planned?

[R0Wi]

@buchdag would you like to see such a feature in this product? If yes, I can provide a conflict resolution for this PR and add appropriate tests. Just let me know 👍

[buchdag]

@R0Wi if documented and tested, yes I'd like to see this feature merged 👍

[Langsdorf]

@R0Wi hey, any updates on this pr?