[Users] Folder features request

[Ian]

I have recently migrated to Claws Mail and there are a few features
from the previous system, on another OS, that I would find
useful. These would all be on a per folder basis.

1) Hide folder - options would be Yes, No, No Unread or No messages.
This would reduce the folder list to make it easier to view. A 'View all
folders' option would be needed to override the per folder option.

2) Announce delivery - using 'espeak' it would announce how many
messages arrived in each box (for folders that have the announce option
ticked). Message would be 'Received <folder name> <number of messages>'.
There might be several announcements if new messages were delivered to
multiple folders.

3) Expiry - option to expire messages to another folder after a number
of days (e.g. the wastebin).