Please add support for nested builders in the DSL

[joshlong]

This could take advantage of lambdas in Java 8.

This would mean we could configure things in Spring Security without worrying about indents.

foo 
  .a ( aSpec  ->aSpec.foo() .bar()) 
  .b ( bSpec -> bSpec x().y())

Spring Integration and Spring Cloud Gateway both support similar nested builder style DSLs.