added class diagrams for db, pos, and pos.storage.  Continuing to work
on Price Check
Updated Price Check
added POS model class diagram. corrected scanactivity to report item not
found in a toast popup
saved the class diagrams as .png so the OjectAid UML plugin isn't needed
to view them:
POS/Class_Diagram.png
POS/src/edu/txstate/db/DB_class_diagram.png
POS/src/edu/txstate/pos/POS_class_diagram.png
POS/src/edu/txstate/pos/model/POS_model_class_diagram.png
POS/src/edu/txstate/pos/storage/POS_storage_class_diagram.png
Merge remote-tracking branch 'origin/chris'