changes to allow multiple choicetextresponses in one problem

This fixes a bug which prevented multiple ```choicetextresponse``` inside of a single problem. Previously the values that were sent to be checked contained a serialized version of all of the inputs inside of a problem, so having two separate input groups would cause extra incorrect values and make it impossible to get the problem correct. This changes so that the submitted value for an input group will only contain a serialized version of the inputs inside of its section.


Also removed an erroneous space from the template.