Big changes (to adapt to my workflow)

[rshk]

Cheers, I'm opening this PR to let you know about the changes I made to make the script work for my needs.

In particular, I needed to be able to run the verification webserver locally, and without the need of stopping the webserver in production.

Plus, since I'm generating certificates for several domains at once, I needed all the signing to be done automatically, to remove some manual processing.

The changes basically boil down to:

• Add support for specifying a port different than 80 for the verification process
• Add support for running the verification http server locally / automatically
• Automatically sign the requests when a user key is specified
• Reorganize the code / one multi-command script to perform all the operations

I preserved all the functionality of the previous script, but the interface changed quite a bit. Not sure if you want to consider merging this inside your project (we'll have to figure out some way to keep backwards compatibility), or I should just make it a separate project..?

(I opened a PR to keep the discussion public, but if you prefer, just feel free to send me an email at the github contact email).

Thanks!