FramePacker sort only *remaining* frames to pack, because when we skip the index forward by the number of frames we packed, we won't necessarily be skipping the correct frames (since we skip in the *UN*sorted array). Instead, sort this.frames at the start of FramePacker process

Exporter now packs all graphics on the same FramePacker, and sends all the pngs back (had to up the string length size to 4 bytes for all the data)

Exporter.fla now grabs sprite-style frames and packs them to sheets (no return data yet)