typo in manual: cipher mode ebc -> ecb

(cherry picked from commit 24f6eb74d414eaa2458909dfe66ac8804228bee0)
Add new -c/-C options.

-c and -C can be used to specify the keychain to switch to, after
database open.
Extend manual accordingly.
Add new regression tests for the blowfish encryption cipher, scrypt KDF
(if compiled in), and the new -c/-C options.

(cherry picked from commit e05fdb646d7a316372902632367c67422565db99)
Extend Changelog with the item removed from TODO.