Remove kv_database_config

[heifner]

Mandel does not use kv_database_config as it is part of Key-Value host functions not in Mandel. This should be removed. Removing it modifies chainbase schema, and snapshot version. May want to consider just marking it as not used and leaving it to avoid having to modify the chainbase schema and snapshot version.

[matthewdarwin]

Or v7 snapshots here we come.... ;-)

[stephenpdeos]

An acceptable short term solution for now will be inserting a comment in the header indicating this is not in use. This will be prioritized for snapshot v7.

[heifner]

Resolved by #753