Add a raw line-coordinate output mode #2

Sometimes I need a decently smart line-based drawing algorithm for an image outside the context of CASIO Basic.

This change adds a raw output mode (-r, --raw) that prints space-separated line coordinates in the (x1 y1 x2 y2) order on stdout rather the CASIO Basic code.

Sample output :

% ./sprite-optimizer.py -r drak.png
16 26 30 25
7 10 7 21
11 21 11 11
5 20 5 11
17 24 23 16
14 2 22 3
0 11 1 19
31 11 31 18
20 15 14 22
8 14 10 21
11 25 21 27
24 5 26 11
... 73 lines total