FAT32 caching

[DrDeano]

Currently, the FAT32 driver will write directly to the underlying stream (could be a RAM disk or a hard disk) when every a write occurs. This would update the FAT, FSInfo and short entry for the file being modified on.
Additionally, when reading files, each time there is a read, the driver will re-seek and re-read the FAT from the stream.
Adding caching to parts of the driver would increase speed.
Caching points:

• Cache part of the FAT (as this can be big) and read new parts of the FAT when needed
• Cache the FSInfo
• Cache file entries
• Cache files entries in a directory