Unit Tests

- Tests now conform to template.
Eval

- Raises an exception if an expression evaluation yields an unexpected
  stack size at the end. This indicates that an expression like 'one two'
  was evaluated. Note that string field updates require evaluation, but
  this case occurs frequently.
Task

- Durations are now stored as-is, with no evaluation.
Task

- All attribute types (number, string, date, duration) are ѕpecifically
  handled, with no default cases.
ColID

- Now uses the standard type 'numeric', instead of 'number'.
ColIMask

- Now uses the standard type 'numeric', instead of 'number'.
ColUrgency

- Now uses the standard type 'numeric', instead of 'number'.