Allow plain HTTP console access (as a non-default option)

We got a report that people were having problems with the fact that HTTPS is used to access the Heritrix3 web console. In some situations, e.g. corporate IT environments, it is not possible to accept self-signed certificates nor import/permit locally minted certificate authorities.

If there are no objections, I would like to propose a new command-line option that enables acccess over plain HTTP. If it is not set, then users should be directed to HTTPS (as per #318). But if this option is enabled, users should be able to access the console directly.

A further question is whether the HTTP Basic authentication should always be required. Certainly, if there is authentication it seems like we must enforce the use of HTTPS. But, we could allow users to switch off authentication when accessing Heritrix via HTTP?

Start by reviewing the Heritrix3 web console's existing HTTPS behavior and the related discussion in #318. Then trace how command-line options and HTTP Basic authentication are configured. Done means a documented, non-default plain-HTTP option with a clearly decided authentication policy and tests covering both HTTP and HTTPS access.

Written by the indexing model from the issue text.