Added full disk partition management functions

Added full disk partition management functions
Extended partitions are supported (untested)
If you call OpenDrive() with Partition == 0 you get the active (or bootable) partition
Partitions 1 - 4 are the primary partitions
Partitions 5 - n are the extended partitions
Also added disk parameter detection code (always assumes 512 byte sector size, I don't like that but I don't see any other way)

svn path=/trunk/; revision=2651