Let's Encrypt: Small improvement suggestions

Hi!

Here a few suggestions for Let's Encrypt certs:

1. UI: Put by default "Auto-Renew" and "2" months so we don't forget to enable it

2. UI (minor): The text-area to enter multiple domain names is not disabled nor does it auto-select the corresponding radio-box when filled-in, leading to possibly inconsistent input

3. Sometimes a server is password-protected, leading to not possible setup of Let's Encrypt certs that need access to the file in that folder. I had to manually add this .htaccess file in the public_html/.well-known/acme-challenge/.htaccess folder:

I'm not sure if for renewals, files need to be added temporarly to the server (do they ?), but in all cases, such a .htaccess file should be as temporary as the token file of that folder.