#17 exe: learn octave distance in staff

[Marek Wieckowski]

This is a simple idea, which could use existing Sfaff
widget (with a few modifications).

The exercise should look like this:
* a range of notes of at least 2 octaves length is shown
* a note (=question) is highlighted
* user has to click on another note of the same name.

When idle (i.e. not during the test) there should be
name-buttons box shown to ease highligthing all notes
of specific name. But during a test this would be
totally disabled.

So, the window would look like in kln2-1.2 staff2name
exercise, but would behave differently.

It would (will?) be an important exercise because:
* current staff2name is completely random; through it
you won't learn to recognize e.g. two same chords, one
transposed by a full octave;
* it's important to learn everything both ways: we
train finding a name, this exercise would train finding
a note in the staff.

==============
Additional ideas:
* all notes should be shown during a test; but
questions should be chosen only from a few (like for
the piano kbd: you don't hide some keys to learn others...)
* question's name should NOT be displyed until a user
answers.
* kbd and speech inputs should obviously be turned off;
also the pitch recognition would be confusing (you
would see a note and would be supposed to ... play
another note?) and shoudl be turned off; the only user
input for this exercise would be mouse clicking.

~Marek