Fix path on pages + Add test for navigation

src/Controller/CapsuleGroupController.php

templates/capsule/delete.html.twig

templates/capsule/editors/list_editors.html.twig

templates/capsule/editors/remove_editor.html.twig

templates/capsule/editors/remove_pending_editor.html.twig

templates/capsule/groups/capsule_groups.html.twig

templates/capsule/groups/create.html.twig

templates/capsule/groups/delete.html.twig

templates/capsule/groups/remove.html.twig

templates/capsule/groups/user_groups.html.twig

templates/capsule/index.html.twig

tests/acceptance/BasePageTest.php

tests/acceptance/CreateCapsuleGroupPageTest.php

tests/acceptance/DeleteCapsuleGroupPageTest.php

tests/acceptance/IndexPageTest.php

tests/acceptance/UserCapsuleGroupsPageTest.php

tests/functional/CapsuleGroupControllerTest.php