Allow a teacher/admin to see the list of modules with controls

[amellie]

Dependency

Depends on #13 and #22

Story

As a Teacher or an Admin
I Want to see the list of existing modules
So That I can see review these modules and perform actions (create/update/etc)

Acceptance Criteria

• The page can be only be accessible by a teacher/admin
• The page should contain a table, showing these columns:
  -- Name (of the module)
  -- Number of lessons related to the module
  -- Action (which contains: Edit and Delete button)
• A Create button should be added to the top of the table. When the button is clicked, it should show the page that has been done in Allow a teacher or an admin to create a new module #15
• Edit and Delete buttons do not do anything when clicked (this will be handled in another task, so please leave it as is)