Support icons.bni and icons-WAR3.bni

[nmbook]

Support downloading .bni files and adding those icons dynamically to support private servers with custom icons.

Parts to do this... is quite a list:

• BNFTPv1 & BNFTPv2 (fully documented here and here)
• BNI parsing (SC/W2/D1):
  • BNI header parsing (partially documented here; though it's not well explained, the header is straightforward)
  • TGA image parsing (documented here)
• BNI parsing (W3):
  • MPQ parsing (documented here - this will probably be the most work)
  • BLP1 parsing (partially documented here; BLP1's are similar to BLP2's but different header, it seems)
• BMP output (documented here)
• adding to ImageList dynamically