SEC-2402: Reference cleanup

* Fix link rendering in CSRF section
* Remove static from MultiHttpSecurityConfig sample
* Decrease indention since can render w/ PDF now
* Remove invalid characters
SEC-2355: Add PATCH to intercept-url xsd
SEC-2355: Add test to validate intercept-url PATCH works
SEC-2350: Remove warning whe using Spring 4
SEC-2373: Update XSD doc to state security="none"
SEC-2350: Fix broken test
SEC-2165: remember-me@token-validity-seconds can be parameterized
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 .