Move all credential check data into html data- attributes so that the JS will also work with multiple plugins. The AJAX calls will simply retrieve the data from the button's attributes, including the ajax url and the list of possible credentials

- Change the counter values to a non-autoloading option
- Clear the option cache before reading the current counter value

Before this change, one order would change the counter value, but a second order submitted while the first is still processed would get the old, cached value and thus generate duplicate order numbers. This changes make sure that the counter is never used from cached values.

Remove year variable from the free version; global/non-global counters are not required in the free version, then, either

Connect the hooks for order action handling in the backend (to assign a new ordernumber to an existing order)

Try to factor out shopware-specific calls from the general number creation code; Fix custom variables

First attempts at implementing the counter editing table in the backend. Display works, JS modifications and AJAX don't.

Try to get order creation in the backend working. FE is still missing a hook when the order is first created

Apparently, sorting by a post meta will not work if the meta contains spaces...
It seems to be a convention to start all post metas with an underscore and separate each word by an underscore, too...