SEC-2411: Update to Gradle 1.9
SEC-2412: Update to propdeps-plugin:0.0.5
SEC-2407: Better error message for missing securityFilterChainBuilders
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 .