begin implementing PodioView

Not quite finished, but allowing code like:

$view = $app->filter['test
view']->sort('fieldname')->cardLayout()->setXAxisField('xfield')
 ->setYAxisField('yfield');

$view->fields['somefield']->from(5)->to(7);
$view->pseudofields['created_by']->user(123456);
$view->pseudofields['last_edit_by']->me();
$view->save();

lots of detail remains to be fleshed out.