Added multi-line ASCII to sprite support

I have added in a function to convert ASCII strings into numeric sprites. It should make it easier to draw out sprites in the program.

The characters still need more thought but the general concept/implementation is there.

```python
"""
 ------- 
-:.._..:-
-..___..-
-:-----:-
--_-_-_--
 -_____- 
  -----  
"""

[
[0,4,4,4,4,4,4,4,0],
[4,3,2,2,1,2,2,3,4],
[4,2,2,1,1,1,2,2,4],
[4,3,4,4,4,4,4,3,4],
[4,4,1,4,1,4,1,4,4],
[0,4,1,1,1,1,1,4,0],
[0,0,4,4,4,4,4,0,0]
]
```