Add quick-add feaure to character-page

[PhilippMDoerner]

Basically, make the item-list on character-page have 2 create options:

1. Link to create-page of given item
2. 1-off drop-down field of all "unowned" items (Means new backend endpoint, new service call in item-service and new method in character-page-store). .If the user selects one and confirms, that sends an http-request to update the item that this character is now the owner of said item.