[html-formfu] new default_args() method - deprecates element_defaults()

[Carl Franks]

I've added a new default_args() method - which basically does what
element_defaults() did, but also for constraints, inflators, etc.

element_defaults() still works for now - it just passes it's args to
default_args()->{elements}
but it issues a warning, and will be removed in a future version.

Here's the POD for the new method:


=head2 default_args

Arguments: \%defaults

Set defaults which will be added to every element, constraint, etc. of the
listed type which is added to the form.

For example, to make every C<Text> element automatically have a
L<size|HTML::FormFu::Element/size> of C<10>, and make every C<Strftime>
deflator automatically get it's strftime set to C<%d/%m/%Y>:

    element_args:
        elements:
            Text:
                size: 10
        deflators:
            Strftime:
                strftime: '%d/%m/%Y'

To take it even further, you can even make all DateTime elements automatically
get an appropriate Strftime deflator and a DateTime inflator:

    element_args:
        elements:
            DateTime:
                deflators:
                    type: Strftime
                    strftime: '%d-%m-%Y'
                inflators:
                    type: DateTime
                    parser:
                        strptime: '%d-%m-%Y'

Note: Unlike the proper methods which have aliases, for example L</elements>
which is an alias for L</element> - the keys given to C<default_args> must
be of the plural form, e.g.:

    element_args:
        elements:          {}
        deflators:         {}
        filters:           {}
        constraints:       {}
        inflators:         {}
        validators:        {}
        transformers:      {}
        output_processors: {}