Added texture configuration, loading and texture mapping to walls

main.cpp: Cleaned the
code a bit, added texture configuration call

common.hpp: New files that contains all the imports and flag definitios

grid.hpp: Fixed ambiguous call to sqrt

room.hpp: Removed unecessary import

wall.hpp: Added code to render with textures instead of vertex colors

textures.hpp: New file to deal with texture configuration and loading from a given file path

textures/: New directory that contains all textures used

models/toyplane.obj: New 3D model added