Fix typo.
Update tests for radio widgets.

Remove tests that will no longer be supported. The between and separator
options have been obsoleted by the templates for radio buttons. Simplify
the remaining tests as the radio widget tests cover the more cases.
Extract helper method for generating radio IDs.

FormHelper tests rely on id's being unique within a set of radio
elements. A separate method will help with that.
Add id suffix generation to radio buttons.

This preserves behavior FormHelper had where it prevents duplicate ids
in a single set of radio options.
Move boolean value handling logic into RadioWidget.

Handling boolean values is part of the widget not the formhelper.
Update FormHelper::radio().

It now passes all the currently unskipped tests related to radio
buttons. Most of the logic has been moved to Widget\Radio and doesn't
need to be in the helper anymore.
Remove tests that are duplicated in Widget\Radio's tests.
Fix indentation.
Merge pull request #2832 from markstory/3.0-radio

3.0 formhelper::radio()