SEC-2357: old RequestMatcher interface extends new RequestMatcher
SEC-2349: Externalize FAQ
SEC-2349: Number the reference
SEC-1932 Added PBKDF2PasswordEncoder.

 - Also moved some logic into a new class, AbstractPasswordEncoder. Both PBKDF2PasswordEncoder and the now-simplified StandardPasswordEncoder extend AbstractPasswordEncoder.
 - Added tests for PBKDF2PasswordEncoder .