[1.4.0] Add support for payees to the app

Currently, categories can be created very flexible in the app. However, some users do not want to create a separate category for each grocery store (e.g. Edeka, Rewe, Netto, etc.). Instead, it would be better to add payees to the app for this purpose, so that the user does not have to create multiple categories (in the example: one grocery category and different payees for each store).

The following functions would be included:

• Manage payees in the settings (sorted + grouped alphabetically analogous to the contacts app)

• Every payee has a unique name

• Optionally, a default account, default category and a default location can be selected for each payee

• Selection of a payee is done in transaction form (e.g. under the account)

• Selecting a payee from the list will then (if set) change the default account, default category and default location (if necessary)

• If a transaction has a payee, this payee will also be displayed in the read-only form

• In addition, it should be able to filter the list of transactions by payees as well