RFC: Simplify/split up FormHelper::inputs

FormHelper inputs is a problematic function.

For example in 2.x:

 * You can't customize one field without declaring all fields.
 * You can't say "give me all fields except <this one>"

In 3.x currently:

 * You can't change the field order.
 * You can only blacklist fields, you can't say "only give me these 2 fields"

In both versions the function wraps the output in a fieldset - which means it's "some work" to not use inputs and still get the same output.

These changes separate functionality into different functions so that users can pick and choose what they want to do/use.

Thoughts?