Added seeds-file
Fixed misplaced thead
Changed page header for exams/index
Changed page header for exercises/index
Reworded courses/index list headers
Eager load everything necessary in courses_controller
Eager load everything necessary in exams_controller
Eager load everything necessary in exercises_controller
Added proper header to exams/show
Added links to single exercises on exams/show
Account for possible null values for answer and criteria in exercises/_list
Added proper header to exercises/show
Fixed LaTeX mistakes in seeds-file
Added custom fonts to main site headers
Added styling for individual exercise links and latex-imagefiles
Centered footer links