Show course content as cards

[fnitu]

For users, the course content should be shown as a sidenav (https://material.angular.io/components/sidenav/overview), the course items inside should be displayed as a tree: https://material.angular.io/components/tree/overview

The course items should contain: icon, name, status and they should ALL be expanded by default.

The sidenav should be collapsible.

Route to be modified: user/course/course/1

[fnitu]

Working on integration of Material tree

[fnitu]

Basic integration was done, working on loading the content when clicking the tree.

[fnitu]

URL to be used for server data: https://edu-hospice-api.herokuapp.com/swagger-ui.html#/user-course-controller/retrieveUserCourseDetailsUsingGET

[fnitu]

@TudorPetruToma Please commit your changes.

@razvantudorache Please take over the task after the changes are committed.

[razvantudorache]