Fixed Group add

Adding groups now retrieves the new ID for the group upon insertion
Database helper optimizations

Added update methods which should be called in the event that a product
or group is updated. This ensures that all changes are seen without the
need for a bulk check during save which is very time consuming.

Fixed groups so that they properly move products when added from other
groups.

Fixed Excel parsing when running on an x64 machine
Renamed ProductsAndGroups to ShopNetcDBHelper

Less easy to mix up with ProductGroup, ProductCollection, etc.
Renamed DBHelper file

Ooops forgot this