Add 40 track support to IDTOM/IMTOD

[hoglet67]

Suggestion from Col here:
http://www.stardot.org.uk/forums/viewtopic.php?p=200617#p200617

"also, when using the program, may be could add a question from DFS>MMC program for 40 or 80 Track, or just press Escape at T41 :)"

[ZornsLemma]

Probably stating the obvious, but you can read the number of sectors from the DFS catalogue to avoid actually having to ask the user how many tracks are on the disc.