2 new exercises for cosine; 4 new exercises (and 1 JavaScript unit)  for Projectile motion

Cosine in the simplest cases: variations with 90º:
exercises/cosine_simplest_1.html
Cosine in the simplest cases: variations with 30, 45, and 60º:
exercises/cosine_simplest_2.html

JS Unit for Physics (only Projectile motion so far)
utils/physics.js
Projectile motion: Constants:
exercises/projectile_motion_constants_1.html
Projectile motion: Time to the highest position:
exercises/projectile_motion_2.html
Projectile motion: Horizontal distance:
exercises/projectile_motion_3.html
Projectile motion: Initial velocity, Time:
exercises/projectile_motion_4.html