Update to 0.7.0

[AetiasHax]

This update adds mutable accessors on the plain Rom type, and adds support for more games.

• Mutable getters to plain Rom fields
  • rom::OverlayTable::overlays_mut
  • rom::Rom::header_logo_mut
  • rom::Rom::arm9_mut
  • rom::Rom::arm9_overlay_table_mut
  • rom::Rom::arm9_overlays_mut
  • rom::Rom::arm7_mut
  • rom::Rom::arm7_overlay_table_mut
  • rom::Rom::arm7_overlays_mut
  • rom::Rom::header_mut
• Don't require HMAC-SHA1 key if overlay table signature is specified
  • Adds compatibility with games with an overlay table signature, but no overlay signatures or HMAC-SHA1 key
• Support multiboot signatures
  • RSA signature at the end of the ROM, used by games that can be shared with Download Play
  • NOTE: Signing is not possible due to unknown private key
• rom::Arm9::libraries to access library strings in the ARM9 program