[Seaside] Nested forms - next solution in ShoreComponents

[Pavel Krivanek]

ShoreComponents-3-pk.2.mcz can work again with nested forms. The
solution is very similar to the solution in ShoreComponents-2.6 but it
doesn't require parent references.

The next little improvement is that ShoreComponents supporting html
code is placed in the special component so applications that cannot
use ShoreRootComponent subclass as the root component can use
ShoreComponents too if they place this component somewhere.

I think that it may be good idea to test this solution of nested forms
 properly and use it directly in Seaside. It helps to create more
general and reusable components.

-- Pavel