Formish

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* Added the errors property to allow a user to get hold of the full list of
errors (including the original validator settings)

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BUG FIX: convert error if a choice type is given bad request data.

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* Added object base class to enable 2.4 comptibility

BUG FIX: made sure the 'empty' attribute worked symettrically (goes with
removing empty string checking from convertish)
BUG FIX: none_option default was empty string which broke when using datetype.
BUG FIX: sequences could not be used as values in select choice

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BUG FIX: Success and Failure callbacks didn't work

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* Added testish tests for default values using radio choice and check box as
booleans

BUG FIX: Radio choice type conversion was broken

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* Added the 'empty' attribute to allow empty values to come back as anything
you like (normally they return None)
* Reviewed the way conversion works and added extra tests.. picked up on a
couple of edge cases

BUG FIX: bugs in the conversion of none_option values