introduces dicts to interface with the treeview
makes treemodel sortable
implements costum sort function
fixes bug, where the toggle column couldn't be sorted correctly
makes necessary changes to the add article function
makes necessary changes to the delete article function
removes debug print
changes header text, so that there is more space for the title column
fixes changed sleep limits not taking effect until app was restarted
roughly fixes various problems, when article becomes N/A
fixes bug, where not available articles wouldn't be sorted correctly
removes left over debug print
introduces alternating row colors for the treeview
adds necessary config options in the config window
config window now resets the checkboxes and spinbuttons when canceling out of it
adds padding on the sides to the treeview
slightly changes the button label for changed my mind