ProjectManager: Add convenience Task subclasses

For Compile, BuildSystem and Deployment. Unclutters user code and reduces
binary size.

Change-Id: Ia18e917bb411754162e9f4ec6056d752a020bb50
Reviewed-by: Christian Kandeler <christian.kandeler@qt.io>

src/plugins/tasklist/tasklistplugin.cpp

@@ -153,8 +153,8 @@ static bool parseTaskFile(QString *errorString, const FilePath &name)
         }
         description = unescape(description);
 
-        TaskHub::addTask(type, description, Constants::TASKLISTTASK_ID,
-                         FilePath::fromUserInput(file), line);
+        TaskHub::addTask(Task(type, description, FilePath::fromUserInput(file), line,
+                              Constants::TASKLISTTASK_ID));
     }
     return true;
 }