docs website: enforce HTTPS connection

While working a lot with the docs website, I noticed that it's still possible to use it with unencrypted http://

This should be changed in the Apache config to enforce a https:// connection.

A valid https:// connection has been supported for a while but it's not enforced – contrary to www.thevirtualbrain.org. Most of the existing links on other websites still target the standard http:// connection.

This small change will benefit the entire TVB online ecosystem:
For years, Google has been preferring force-encrypted websites decidedly when indexing pages and deciding how to rank search results.

In Analytics, the indexing importance and traffic of the docs website has been clearly visible since like forever.

If we only get a small upgrade from Google, all interconnected TVB and TVB-related websites will get a slice of this cake.