rework attach to require explicit key
64k iterations plus pragma cipher_default_kdf_iter function
Merge branch 'prerelease' into attach
Merge branch 'prerelease' into kdfiter

Conflicts:
	src/crypto_impl.c
Merge remote-tracking branch 'origin/prerelease' into kdfiter
finalize new attach behavior

- key can be specified in hex as key plus salt together
- source passphrase is cleared after derivation
- key specification containing derived key and salt stored on
  cipher_ctx for use in attach on an encrypted main database
  when no key is provided with the attach statement
Initial work on a PRAGMA cipher_migrate

Swapping of the Btree meta data is not working properly now.
More work on cipher_migrate, still unusable
Swap btree for write, reset password on codec - working.
Clean up compiler warnings
Work to configure the proper env. for the migration
Attach new codec before btree copy
Add tests for cipher_migrate
null termination of key value
Adjustments to cipher_migrate

- And format flags when checking for exit condition
- Pass key size to sqlcipher_check_connection
- Trace version upgrade logic
Merge branch 'attach' into kdfiter

Conflicts:
	test/crypto.test