Fix viewing all parts
Tweak changelog entry
[mms] Rewritten/improved linked attachment code.

Reduce overall storage space in VFS backend - single folder contains
all attachments for a user rather than a new folder for every
message.

Additionally, there is now a single metadata file for a user rather than
(potentially) one metadata file per attachment. This should also speed
up the pruning login task (vastly reduces the number of VFS calls needed
to determine whether a file is expired).

This metadata file now contains the timestamp and the MIME type (the
MIME type no longer needs to be determined dynamically every time the
file is downloaded).

Stream the file to the browser to reduce memory usage.

Attachments are now accessed by a UUID rather than a potentially
complicated filename.

Backend logic now lives in library rather than display script.

More details are now displayed to the receiving user regarding the
attachment contents.
IMP_Mailbox_Ui::getSize() -> IMP::sizeFormat()
update package.xml requirements
Use injector to determine if mail logging is available