The ability to create backups using the ForestDB storage format should be removed

ForestDB has been marked as depreciated for a while now and will no longer be supported by cbbackupmgr. For this reason (and several others) collection aware backup restore will only be supported for SQLite. We do however, still need to retain the ability to read from (and therefore merge) users existing backups which use the ForestDB format.

How will we achieve this change?

The storage format we use must conform to the 'BackupFile' interface; this constricts us to having only read write storage formats, therefore, the 'BackupFile' interface will be replaced with the 'BackupFileReader' and 'BackupFileWriter' interfaces. This will then mean a large portion of the ForestDB codebase can be stripped away.

What  are the benefits of this change?

1) We no longer have to support two different backup storage formats (collection aware/unaware).

2) When it comes to writing stats (on 'DataBackup' Close) we can do so in a collection aware fashion without having to support writing collection unaware stats files (we should still be able to read them for backwards compatible use of the info/list commands).

What are the consequences of this change?

1) Users will no longer be able to force the creation of ForestDB backups using the hidden 'storage' flag.