Replace ATTACH, SELECT, DETACH with sqlite3_key and sqlite3_rekey

[sjlombardo]

@pdp - no, you can’t use sqlite3_rekey to encrypt a standard (plaintext) SQLite database. The only supported way to do that is via ATTACH and sqlcipher_export(). See here for more details:

How to encrypt a plaintext SQLite database to use SQLCipher (and avoid “file is encrypted or is not a database” errors)

We often field questions about how SQLCipher encryption works. In one common scenario, a developer wants to convert an existing standard SQLite database to an encrypted SQLCipher database. For example, this might be a requirement for an application that was not previously using SQLCipher, and must convert an insecure database to use SQLCipher full database encryption during an upgrade. In such cases, developers may initially attempt to open a standard SQLite database and then call sqlite3_key o…