Fix input() making multiple checkboxes.

If you used the new input type name the output would be incorrect and
a notice error would be triggered.
Fix radio widget and label=false.

Use some strpos tricks to handle the situation where nesting labels are
being used but label=false.
Fix missing label elements in input(type=radio)

This makes radios like multicheckbox where an additional label is output
for the group of radio buttons. This label has a not entirely correct
for attribute. I've also added tests for label=>false scenarios.
Remove meaningless and possibly wrong for attr.

The generated for attribute for input group labels was pretty much
always wrong. Instead of trying to make it correct just omit it.
Remove for attributes for other group type inputs.

date/time/datetime inputs have long had their for attributes wrong as
well. Lump them in with other group type inputs that no longer get for
attributes that are just wrong.
Merge pull request #5006 from cakephp/fix-radio-multi-checkbox

Fix radio & multicheckbox