Feature/encrypted profile boolean values

Resolves issue #176 - This also adds support for setting the boolean to nil or blank.
just call value_to_boolean above.

also, vlaue_to_boolean already has a case where it returns nil ...  
	def value_to_boolean(value)
	  if value.is_a?(String) && value.empty?
	    nil
	  else
	    TRUE_VALUES.include?(value)
	  end
	end

can we use that?