page: replace global variables by $Page object

page: replace global variables by $Page object

Former $Article is sufficient to provide all derived values:

	$Page       = $Page->handler
	$Args       = $Page->path
	$PageAccess = $Page->restricted
	$Article    = $Page

Swap with more appropriate (and short) $Page name and replace any usage.
Major incompatible cleanup before other upcoming behavioural changes.