mail_daemon: Converted to BServer.

Mail server: fix disabling notifications

* The default notifier didn't always take the setting into account.
* The mail server was not using the setting from the settings file and
instead waiting for a message that wasn't sent anywhere.

Fixes #10852.

mail_daemon: cleanup, 30s auto check startup delay.

* Refactored new message retrieval a bit, so that the notification strings
aren't duplicated.
* The daemon now waits 30 seconds before doing the first mail check.

Renamed MailDaemon{App|.cpp|.h} to MailDaemonApplication[.{cpp|h}].

Mail server: fix disabling notifications

* The default notifier didn't always take the setting into account.
* The mail server was not using the setting from the settings file and
instead waiting for a message that wasn't sent anywhere.

Fixes #10852.

mail_daemon: cleanup, 30s auto check startup delay.

* Refactored new message retrieval a bit, so that the notification strings
aren't duplicated.
* The daemon now waits 30 seconds before doing the first mail check.

Renamed MailDaemon{App|.cpp|.h} to MailDaemonApplication[.{cpp|h}].