wipeLocal

Clear out locally stored logins data

If sync is enabled, then we will try to recover the data on the next sync.

The main reason to call this is when regenerating a new encryption key. In that case, there's no reason to keep around the local data since it can't be decrypted. Calling wipe_local is better than keeping around these un-decryptable logins, since we might be able to recover the data via sync.

This is a no-op for freshly created databases, so it's safe to call this whenever a key is generated.