Improve using scopes for user commands

Background

The user:create command without arguments is broken, since the introduction of user scopes.
The working of user:password:change is unsure when a username is used in multiple scopes.

Requirements

• Use the Integrated scope for the user:create and user:password:change command, when no scope is specified
• Add the scope as optional argument for the user:password:change command (when not specified use the Integrated scope)
• The "user:create" command currently adds a new scope admin scope when the specified scope does not exist. This is not OK, only one admin scope can exist. Please create as a non-admin scope, or prevent using scopes which not exists.

Test scenarios

• Set up an installation with multiple scopes
• Use the user:create command to create a user --> it should be created in the Integrated scope
• Use the user:create command to create a user x on scope x --> User should be created in scope x, unable to login into Integrated
• Use the user:password:change command to change user x --> should not be able to find user, password should not be changed
• Use the user:password:change command to change user x on scope x --> password should be changed
• Create a duplicate username (on different scopes) and use the user:password:change command on scope x. Only the user with scope x should be changed