Add libkv::export and libkv::import functions
Description
Users need to be able to export stored information from a key/value store and then import it into a different key/value store. This ticket is to create libkv functions for that capability and then implement them in libkv's file store plugin.
The export should have two modes:
Export all data
Export an environment's data plus any global data.
Acceptance Criteria
None
