Updating UML with new Data Manager classes
Updating UML from feedback received.

Add IUpvotable and ICommentable.
Add `AttachmentItem`, `AttachmentController` UML
Adding activities and observable models.

Changed IUnique to QAModel class that implemented notifying views.

Added QuestionViewActivity, QuestionTaxonomyActivity, QuestionListActivity
activites, and QAItemAdapter list adapter.
Changed IUnique to QAModel organized views.

We had forgotten that the models needed to support notifying of observing
views, and thus shouldn't be an `IUnique` interface.
Generating PDF of UML diagram.
Renaming QAItem to AuthoredTextItem.

To reduce possible confusion with `QAModel`, and to better reflect its
purpose.
Cleaning up visio diagram.
Updating UML with new relationships and adding descriptors.
Merge pull request #46 from Mobius5150/uml

UML Class Diagrams