AFF sector annotations.

Why? Becuase there are many cases where we want to annotate on a sector-by-sector basis:
     * Bad blocks
     * Blank sectors
     * Accessed sectors.

Functionality we want:
 * Set annotation
 * Query
 * Find sectors with an annotation?

Model: A 1TB disk has 2 billion sectors and 62,500 AFF pages (wow;
       what happens to AFF performance when all of that is stored in a
       sequential, unsorted list?)

       If we store these annotations as a byte array, that's 2GB for the 1TB disk. Not acceptable.
       Storing it as bits is 256MB; still pretty harsh. 

       Store the annotations per page and you have 4096 bytes with a 1-bit annotation.
       	     - That's okay for a bad block list.
	    for a byte annotation per sector, there are 32K 512-byte sectors on a page.         

       Another option: Store as a sequence of [start block, run length, annotation]
       	       - Good for sparse, bad for filled.
	       - So you would need a way to turn the sparse into non-sparse