Rework creating a bill(WIP)

[Morvvvv]

Creating a bill should follow this flow of actions:

• Choose between an existing group, or no group
• Openadd items screen:
  • contains the following objects:
    • item name and price field
    • bill name field
    • bill date field
    • add item button
    • save button
  • if only one item is added, bill automatically takes the items name as the bill name
  • if more items are added, bill name has to be set by user
  • upon pressing the add item button, another set of item name and price fields will appear
  • upon pressing the save button, the bill will be saved and added to a group, if one was chosen
    • if no name was chosen and more than one item exists in the bill, user is asked to choose a name