Add browser-side checking for max attachment number
Check for max attachment size should also include limit from imp config
Fix some random text that miraculously didn't cause a parse error
Yikes. Default for attachments should NOT be linking

Not sure when I messed this up
[mms] Removed compose 'use_vfs' configuration option.

If VFS is configured for Horde, always use it for session expiration
drafts. That's a core feature and no reason to have to configure it.

That's all use_vfs worked for (it didn't affect VFS storage of linked
attachments, so at best it was confusing).