Fix issue where receiving emails, and we send update emails async

- The process completes before the async threads complete their emailing
Add file description to the details of files in files module
Fix outgoing message id

Cherry picked from https://github.com/ChALkeR/redmine/commit/187ba876aa32f754e906e2124f4e57dbb5af7c92

Without this fix, if one configures Redmine to use something like «Redmine <redmine@example.com>» as the outgoing address
(which works nicely, except for the message-id), the message-id is set to invalid string like <redmine.journal-numbers@example.com>>
because of the invalid hostname extraction.
This results in Google ignoring the invalid message-id field and replacing it with an autogenerated one.
The message then fails DKIM check and goes into the spam folder.

This commit fixes invalid message-id generation, and everything works fine for me now.
Merge commit 'ed2b8e1ccff4ebfe3f9cbbeb635db6060dfad4ad' into rx

add message id fix
Merge commit '742f7c63d395bc92c4eb8710d2e03d1a4e491e23' into rx

Bring in async fix
Merge commit 'a317d8a9da0071816a7ad094094c59b9caa1e0a5' into rx

Add descripts to files