Unified description of the treatment of 0 and NaN.
More precise docstring.
Using the "n" format type in "uncertainty control" mode now raises an exception. Before, I think it just gave a result that was not formatted with the "n" format type at all.
Additional example of non-uncertainty controlled mode.
Commit before major change in the logic of __format__() (implementation of the new docstring).
Switched to having the mantissa of the *nominal value* to always be between 1 and 10. This is more "continuous" (when the standard deviation passes the (absolute value) of the nominal value), and also matches the usual float (no uncertainty) exponent.
Finished simplifying the rules for the exponent notation (nominal value always used).
Review of __format__ complete. Restored the previous code: digits_limit is actually important for calculating the exponent (for the eEgGn format types).
Removed obsolete parameter documentatoin.