unflatten (ods format): booleans are converted to numbers

[duncandewhurst]

This breaks roundtripping JSON <-> ODS.

Test data:

{
  "main": [
    {
      "a": true,
      "b": false
    }
  ]
}

Command:

flatten-tool flatten test.json -f ods

Output:

a	b
1

Expected output:

a	b
true	false