Updates to lecture examples and some documentation fixes

.gitignore

irlc/ex02/dp.py

irlc/exam/readme.md

irlc/lectures/lec02/lecture_02_keyboard_pacman_g1.py

irlc/lectures/lec02/lecture_02_optimal_dp_g0.py

irlc/lectures/lec02/lecture_02_optimal_inventory.py

irlc/lectures/lec03/ex_03_search.py

irlc/lectures/lec03/lecture_03_alphab.py

irlc/lectures/lec03/lecture_03_dotsearch_astar_manhattan.py

irlc/lectures/lec03/lecture_03_dotsearch_bfs.py

irlc/lectures/lec03/lecture_03_dotsearch_dfs.py

irlc/lectures/lec03/lecture_03_dotsearch_dp.py

irlc/lectures/lec03/lecture_03_dp_gridworld_short.py

irlc/lectures/lec03/lecture_03_expectimax.py

irlc/lectures/lec03/lecture_03_frozen_lake.py

irlc/lectures/lec03/lecture_03_frozen_long_slippery.py

irlc/lectures/lec03/lecture_03_harmonic.py

irlc/lectures/lec03/lecture_03_minimax.py

irlc/lectures/lec03/lecture_03_squaresearch_bfs.py

irlc/lectures/lec03/lecture_03_tricksearch_astar.py