Use loop to add items to WBItemStore

Repetitive code was being used in init method of WBItemStore to add file resources to WBImageStore.

* Use a loop to add images to WBImageStore.
* Rename all image files to ItemName.jpg.  This is now required.
* Deleted redundant directory Imgs/.  All image resources in WhichBill/Imgs/
* Added new images for more items; will be implemented later.