fixings and improvements

dev:
- add documentation
- main() is more readable

fix:
- unmanaged errors:
  - map parsing: error if color value is >255
  - map parsing: load_textures(): check return value of xml_xpm_file_to_image()
  - main.c: draw_screen(): check return value of mlx_new_image()

other details:
- dev: color_from_rgb(): change signature
- fix: nullize map in map_destroy
- change: change error message for read_all_text() errors
- change: change rotation speed
- change: add and use contant NOOBONUS_SPEED

testmaps/good_reallyweirdblank.cub

@@ -1,13 +1,13 @@
-F        255,  127  ,0
+F  		 255,  127	,0
 
 C	0,   2  ,	67
 
 
 
-EA     textures/east.xpm
+EA   	  textures/east.xpm
 NO textures/north.xpm
 
-SO  textures/south.xpm
+SO  	textures/south.xpm