Refactor existing BlowfishEngine to allow extension of key schedule and support 'salt' mixing during key schedule table processing.
This allows reuse of most of the Blowfish implementation (only key schedule differs for bcrypt EksBlowfish variant).

Supports 2, 2a, 2b, 2y variants, but not 2x or 'safe 2a' from openwall crypt_blowfish.
Passwords from 0 to 72 bytes supported.
Cross tested with JBCrypt and crypt_blowfish.

…onstructor for legacy/unrestricted operation.