Allow checkbox without an assigned value attribute
Tests for radio/checkbox defaulting to "on" if no value specififed
Revert "Allow checkbox without an assigned value attribute"

This reverts commit e7b483ae55db7f5775b0d9dbd1123a8bb0436cc1.
value of checbkox/radio defaults to "on" when not specified
Merge pull request #1180 from twalpole/pr/1159

Allow checkbox without an assigned value attribute