Need persistent storage system other than config_*

Config framework is good for... configuration items, however we should have a persistent storage mechanism that allows us to store binary data into FCB. Also, FCB should be able to be shared between config, and this more general persistent storage mechanism.

Persistent storage mechanism should support binary data, and writing + appending to entries.

Start by locating the config_* framework and the FCB implementation referenced in the issue. Determine how a shared persistent-storage mechanism could support binary entries, writing, and appending, then define what completion would require for storage and config to use the same FCB.

Written by the indexing model from the issue text.