pokered: pic de/compression.
1:1 conversion for pics.
Add "norepeat" and "arrange" image attributes.

Eliminates repeated tiles and also spits out a tilemap respectively.

One-way for now. Likely to be used in pokered, but useful in its own right.
gfx: Don't pad images smaller than a tile.

Also fix a bug where images smaller than a tile are not converted at all.
Optimize pic compression to be 50% faster.
Clearer explanation for porting https://github.com/magical/pokemon-sprites-rby to python 2.7.
gfx: Transpose blocks of images instead of only the first block.

This allows transposed images to be grouped together (e.g. animations).
gfx: Decompress graphics that can be converted to png.

Before, converting a .2bpp.lz file required calling decompress and convert_to_png
on the compressed and decompressed files respectively.

gfx.py unlz {}.lz
gfx.py png {}

Putting a .lz file into convert_to_png would raise an exception.

Instead, passing compressed graphics into convert_to_png will decompress them first.
This skips the (now optional) manual decompress step.
Merge pull request #72 from yenatch/pics

pokered: pic de/compression.
gfx: Don't try to load baserom.gbc unless it's actually being used.

This prevented pokered from building if the file "baserom.gbc" did not exist.
Transpose images by height from 2bpp to png and width from png to 2bpp.

Transposing non-square images would work over the expected width, rather than the current width (the expected height). This never came up since transposed images are typically square.