Improve usability of CiviMail configuration screens & integrate with core configuration checklist

For the context on this issue, see http://forum.civicrm.org/index.php/topic,12730.0.html.

I think that there are too many places in the CiviCRM Admin interface to specify email addresses & domains. When you have an existing CiviCRM install that works, and you need to change the address for the mail server to get the backchannel to work, it is unclear whether you should go to Configure: Domain Information; Configure: From Email Address; CiviMail: Mailer Settings; CiviMail: From Email Addresses; or CiviMail: Mail Accounts.

Part of the confusion is because CiviCRM core email settings & CiviMail email settings are different. Perhaps there should be a cross-link on the Domain Information page that shows up when CiviMail is enabled, so people know that they need to its configuration pages also. In addition, I like the checklist that exists for the core settings. Would it be possible to conditionally include links to the optional components' configuration on that page? (For example, the mail settings pertaining to CiviMail could appear below the other mail settings.)

As for the pages in the CiviMail component themselves, I think Mailer Settings & Mail Accounts should be merged into one form, called Mail Settings. The Mailer Settings options could appear at the top in a fieldgroup called Global Settings, and the Mail Accounts settings could show in a list called Mail Domains below (with the settings for each editable either inline, or on a separate page). If it is too difficult to merge the pages, there should at least be help text cross-referencing Mail Accounts from Mailer Settings and explaining why it is needed. I initially gravitated toward Mailer Settings, without knowing why I would need to touch Mail Accounts.

Also, it is confusing that CiviMail: From Email Addresses and Configure: From Email Addresses are links to the same page. It should probably only show up in the CiviMail section, since it is used with CiviMail. And it should say something like "the From email address settings do not affect the VERP addresses (which handle bounce-backs, opt-outs, etc.) unless the override option is set".