Add a test suite to cover refactoring the module.

Add a test suite to cover refactoring the module.

This time the test suite concentrates on the external interface. The
way the Horde_Notification test suite was set up was indeed quite
problematic.

The next step for the refactoring would be to extract the Horde specific Elements into a Horde_LoginTasks_Backend_Horde class. This should provide links into the preferences system, session storage, authentication, etc.

The test suite covers one bug: The recurrence calculation for weekly recurring tasks.

There are two tests that are marked as incomplete: I currently still fail to understand the LoginTasks_Tasklist logic that uses the private _addTask variable. Depending on the task order some tasks will get displayed or not. But I don't see the rationale behind it. But the area should see no modifications during refactoring.