Allow injecting root certificate validity via env and also validity for new certs, when using USE_LOCAL_CA=1

[chreniuc]

I added support for controlling the validity of the root certificate and the new certificates, when using local CA(discussion started here: #225).

I tried as you proposed, to generate a root certificate with a longer validity by changing the script and running it outside of the container. It worked to generate a root certificate with a validity bigger than 30 days. But when the container is running, it defaults to 30 days for new certificates, because it uses the script from the container, which has hardcoded 30 days in the openssl_cnf that is also used when generating a new certificate.

I also documented the newly added envs, ROOT_CERT_LOCAL_CA_VALIDITY and NEW_CERT_LOCAL_CA_VALIDITY.

[JonasAlfredsson]

Sorry for slow response, but I have finally have time to look at this.

I am not entirely sure I want to make it so easy and obvious to change this variable. Instead of forcing my ideas into this pull request I have created another one which I would love your feedback on: #230

[chreniuc]

Replaced by #230