Clean up option (default) value access
Currently, the only user for valueCount() and formatValue() in
OptionInfo was actually interested in the default values, and limiting
access to the default values only makes the responsibilities clearer.
So replace both methods with a single method that returns just the
default values. The internal implementation currently places some
limitations on when this can actually be called, but that should not be
a problem for current or future uses.
Change-Id: I3e68ce397ec3f40f62ececad4ee6b87d0ecc790e