Split AssFile into separate lists for each section
Remove some cruft from TextFileReader
Make the entry lists be of the appropriate type rather than just AssEntry

Eliminates a bajillion dynamic casts.
Change AssFile::Info to a vector
Don't return a const std::string from GetData

It has zero benefit and forces an extra copy.
Remove AssEntry::Clone
Move the intrusive list hooks to the concrete entry types
Devirtualize AssEntry::GetEntryData
Make AssFile::Attachments a vector
Fix non-pch compilation