[Feedback requested] Remove webMail element from configs

[cketti]

We want to clean up the config files to only include elements that Thunderbird supports. One element that Thunderbird is very unlikely to ever use is webMail. So we'd like to remove it.

But we don't want to break software relying on this information. If you are the author of such a software, please let us know in a comment, so we can work out a removal date that allows you to migrate to a different database or mechanism.

Example of a webMail element:

<webMail>
  <loginPage url="https://accounts.google.com/ServiceLogin?service=mail&amp;continue=http://mail.google.com/mail/" />
  <loginPageInfo
    url="https://accounts.google.com/ServiceLogin?service=mail&amp;continue=http://mail.google.com/mail/">
    <username>%EMAILADDRESS%</username>
    <usernameField id="Email" />
    <passwordField id="Passwd" />
    <loginButton id="signIn" />
  </loginPageInfo>
</webMail>