Dependency display

Task views now include the list of dependencies and reverse
dependencies. In addition, it is impossible to mark a task as completed
if it has unsatisfied dependencies, and it is impossible to re-activate
a task that has completed reverse dependencies.

includes/t-tasks/page_controllers.inc.php

@@ -150,7 +150,10 @@ class Ctrl_ViewTask
 		}
 		$page->setTitle( $task->title . ' (task)' );
 
-		$result = array( Loader::Ctrl( 'task_details' , $task ) );
+		$result = array(
+			Loader::Ctrl( 'task_details' , $task ) ,
+			Loader::Ctrl( 'task_dependencies' , $task ) ,
+		);
 
 		if ( $task->completed_by === null ) {
 			array_push( $result , Loader::Ctrl( 'add_task_note_form' , $task ) );