Make usage of the Jenkins Credential Plugin instead of username/password and manage configuration by id instead of name

Instead if using separate username and password for each share, it would be nice/better to store the credentials (username/password) centralized in Jenkins, making updates of username/password for a share much easier, especially when some organization needs to update their password against a share for each third months.

Second, instead of using the name as the primary key, its better to use a id, making it possible for end users to change a shares name, without having to update the jobs to point to the 'new' name of a share.

Feedback wanted :)

Best regards
/Jonas M
This looks like it will break backwards compatibility. Why not add a @Deprecated and create a new constructor, just in case.