Add QuickReply

[dlemstra]

This issue is part of #11 and describes what should be done to create QuickReply:

In the folder Messages\Shared and new class called QuickReply should be created. This class should be in the Line namespace. This class should also have a Validate method. An example of this method can be found in some of the other files. The items array should be called Actions and this should also be validated.

After this class has been created it should be added to all the messages as an optional property.