Modify to work with more disk formats

[geby]

Extend drive geometry by a sector size and allow to change drive geometry on the fly. It is good to work with non-PC disks and not need to create a new drive geometry for each obscure format. This code allows to work with sector size 128, 256 and 512 bytes. I am not sure, if track format code working well, however reading and writing sector is OK.

It can ignore disk side mark on sector header search, because some old systems does not using it correctly. (optional feature by define IGNORE_SIDE_MARK)

Added defines to change header seek timing.