Implemented collision detection of Mirrors in contact with Obstacles.

To ensure that Mirrors do not overlap with Obstacles, collision detection
was implemented to check if any of their fixtures are in contact. Once
contact has begun, the Mirror will turn red which signifies that it is in
an invalid position. When the Mirror ends contact, it returns to its
original color. If the Player let's go of the Mirror while still being in
contact, the Mirror is destroyed.