* secret_store: remove kvdb_rocksdb dependency
* cli: init db mod for open dispatch
* cli: move db, client_db, restoration_db, secretstore_db to a separate mod
* migration: rename to migration-rocksdb and remove ethcore-migrations
* ethcore: re-move kvdb-rocksdb dep to test
* mark test_helpers as test only and fix migration mod naming
* Move restoration_db_handler to test_helpers_internal
* Fix missing preambles in test_helpers_internal and rocksdb/helpers
* Move test crates downward
* Fix missing docs
* cli, db::open_db: move each argument to a separate line
* Use featuregate instead of dead code for `open_secretstore_db`
* Move pathbuf import to open_secretstore_db
Because it's only used there behind a feature gate
* Move client DB opening logic to CLI
* Move restoration db open logic to CLI
This adds KeyValueDBHandler which handles opening a new database, thus allow us to move the restoration db open logic
out of ethcore.
* Move rocksdb's compactionprofile conversion to CLI
* Move kvdb_rocksdb as test dependency for ethcore
* Fix tests due to interface change
* Fix service tests
* Remove unused migration dep for ethcore
