SEC-2107: Fix Javadoc on methods of AbstractAuthenticationProcessingFilter

Both overloads of
AbstractAuthenticationProcessingFilter.successfulAuthentication()
claimed to invoke SessionAuthenticationStrategy, which is not true, as
the invokation happens earlier in doFilter(). The Javadoc on these
methods are updated to reflect the actual code.
Merge pull request #22 from zagyi/SEC-2107

SEC-2107: Fix Javadoc on methods of AbstractAuthenticationProcessingFilter
Merge branch 'add-headers' of https://github.com/rwinch/spring-security into add-headers
- Added RNC file instead of XSD directly
- Added/Updated documentation.
Merge branch 'add-headers' of https://github.com/mdeinum/spring-security into add-headers