Add support of ID extension in IMAP

Hi there.
Would K-9 add the support of ID extension in IMAP in the future? Someone else has already post the problem in the GitHub issues.

This extension is defined in RFC 2971
I know it sucks because the 163 mail(Netease) doesn’t follow the RFC standards, but considering that 163 mail has a lot of users(mostly in China), I think it would be more convenient.

 Servers MUST NOT deny access to or refuse service for a client
 based on information from the ID command.  Clients MUST NOT refuse
 to operate or limit their operation with a server based on the ID

For your information, the built-in Mail app in Windows 10 works well with the 163 mail, so I guess the ID extension is implemented in it.