MC7000: Fix off-by-one indexing in the controller script

[fwcd]

Almost the entire script indexes arrays with deckNumber (which ranges from 1 to 4) rather than deckOffset (which ranges from 0 to 3). This works since JavaScript implicitly lets the user assign to out-of-bounds indices:

var xs = [0, 1, 2, 3];
xs[4] = 4;
// xs == [0, 1, 2, 3, 4]

Since most of the script doesn't care about the initial values, this bug doesn't affect the actual functionality much, since JS is happy to use indices 1-4 instead and ignore the value at index 0.

This behavior is subtle and unintuitive, especially with regards to the default values, therefore this PR fixes the script to use the correct indexing (from 0 to 3).

[ferranpujolcamins]

Hi @fwcd , thanks for improving this details! I agree it's clearer now.

LGTM