Added local task to add new carousel items. Added missing carousel admin page title.
Added local task to add new Group items. Added missing Group admin page title.
Added local task to add new Sponsor items. Added missing Sponsor admin page title.
Fixed usage of capital letters.
Merge pull request #20 from zero2one/feature/Add_add_links_to_the_custom_content_admin_pages

Feature/add add links to the custom content admin pages