[2.2] Allowing redefinition of components

[Carsten Ziegeler <cz...@apache.org>]

Currently it is possible to define a component for a role more than
once. While this at first might look like in error, I think it's an
essential feature :)
We already "ship" Cocoon with all required components predefined in our
xconf files. You can customize these predefinitions by using properties
which is great. But what if you want to swap the implementation? You
could start removing the xconf in question and replace it with your own,
but obviously this can't be the answer.
If we allow redefinition, you can simply drop your own xconf with a
component definition for the same role into the xconf directory and this
one will override the predefined one. No need to patch or remove.
In order to make this work reliable I just added the ordering of xconf
which means all xconfs in the same directory are now read in
alphabetical order.

Carsten
-- 
Carsten Ziegeler - Open Source Group, S&N AG
http://www.s-und-n.de
http://www.osoco.org/weblogs/rael/