Task: Clean up default formatting of the attributes as arguments for modify command
Task: Clean up default formatting of the attributes as arguments for modify command

In the current version, we were not properly making difference between value
which is False when converting to boolean, and proper empty value. Thus user
would be unable to save legitimate False-like values into TW, like numeric 0.

robgolding/tasklib,tbabej/tasklib,robgolding63/tasklib