add optional basic auth

[AlbertoGarciaFdez]

Hi, I really love the cli, but i need to use basic auth on the requests, so here is a PR to allow optional basic auth from cli and config file.

I used session requests so it comes easier to modify parameters that are being used on every request, i.e if someone needs to add another optional auth type on the future, just change it on the session.

WDYT?

[tomerschwartz24]

Why is this not merged? what's the point of aptly cli in CI without basic auth