Usage:

create locations, categories first
Then create columns
Then create products and assign columns to them, and assign the product to a specific category.

Meaning for column restrictions when creating a product:
* obligated: this means the value of this column needs to be a non empty value when filled in by a user
* product only: this column is only visible to the product definition, not to the items you create for this product. This might be usefull for a product description, delivery times, ...
* fixed value: when this is choosen, the value filled in next to it will be the only one the user can see when creating an item. Might be usefull when specifying eg. the size of a screen for a product, ...
Remark: when changing a product, all items are scanned to see if they have any columns that should be added/updated/deleted to them. So you see this is a expensive operation when many items are in the db for this product, and this might reult in php timeout here ....

Disabled product:
when this is choosen, no new items can be created anymore for this product (usefull for eg. end of life of a product)

Column creation:
* each column has a unique title, and (if wanted) a default value.
* For dropdown columns, you need to specify possible values seperated by a comma. If you want the first value to be empty, put a comma at the beginning. Eg:
normal dropdown: poss1,poss2,poss3
dropdown with first value empty: ,poss1,poss2,poss3
* for sqldropdown: you need to specify the SQL command here, eg:
SELECT name from fabrikant;
* size: (only for varchar) this defines the width and maxlength of the line
* SQL link: (only for sqldropdown) this is the name of the column you're selecting (in my example this would be "name", without the quotes)


After this you can create items for your products, and assign them a location as well.

If you don't need product definitions, then just create a general product with everything allowed for the columns.
