[html-formfu] incompatible change to plugins

[Carl Franks]

I've had to make a change to the plugin system.

Previously, during a call to $form->process(),
all plugins' process() methods were called,
then all elements' process() methods were called.

Now... all plugins' pre_process() methods are called,
then all elements' process() methods() are called,
then all plugins' process() methods are called.

This will only effect people who've created their own plugin class
that has a 'process' method, that relies on any elements' process()
having not yet been called.
If that's the case, you'll need to rename the plugin method from
'process' to 'pre_process'.

This won't affect the only core plugin; StashValid; as that uses the
post_process method.

I'll add a warning to the next CPAN release's Makefile.PL, so people
are warned, and I'll flag it up in the Changes file.

Sorry for any inconvenience.
Carl