Replace .pic with .png.

Compression is 1:1, so they're interchangeable.

The drawback is this inflates the first build time.
We've agreed that this is worth having pngs out of the box.
Convert pngs in gfx/ to 1bpp and 2bpp.

All graphics are now png.

Some files were split out of necessity:
- gfx/trade.2bpp -> gfx/game_boy.norepeat.png gfx/link_cable.png
- gfx/red/introfight.2bpp -> gfx/red/intro_nido_{1,2,3}.6x6.png
- gfx/blue/introfight.2bpp -> gfx/blue/intro_purin_{1,2,3}.6x6.png
Remove "globals.asm" from .gitignore.

globals.asm is no longer part of the build, is not generated, does not exist at all.
Add *.1bpp, *.2bpp, *.pic to .gitignore.

These are now generated by the build.
Fix tile padding for house and ship_port tileset graphics.
Image handling in the makefile.
Accidentally added a second minimize graphic.
Bump pokemontools for png manifest destiny.

Now the past 10 or so commits actually work.
Merge remote-tracking branch 'yenatch/png'