Allow to select user for which a shared document should be uploaded

[astubenbord]

Allows a user to choose the account for which the document should be uploaded.

Scenario: Multiple users are logged in
    When user shares a file
    Then app opens
    And user selects account from which to upload file
    And account is switched
    And file is added to user specific queue
    And file is consumed
    And file is uploaded
    And app is closed

Scenario: A single user is logged in
   Then use current implementation

A default account can also be specified, which skips the first scenario and always uses the configured user for uploading files which are shared with the app.