in the createIssue() method, a list of all labels is put in the model
Added a new named querry for retrieving all existing labels.
Added a method to IssueService for obtaining all labels.
Now the create-issue page displays correctly the labels.
Now when a user click on the 'create' button, the id-s of all selected labels are send to the createIssue method from issueTrackerService
Changed the prototype of createIssue method from issueTrackerService, now it also contains a list of integers , represnting the id-s of all selected labels.