Scoring fix

This commit fixes problems in the inconsistent rounding of scores reported to students and professors. See the issues raised in the forum post http://webwork.maa.org/moodle/mod/forum/discuss.php?d=3464.  That post also has details on testing the changes.  Specifically create two sets.  The first with a single problem with 8 parts (e.g. Library/272/setStewart14_5/problem_3.pg) and the second with 8 problems (e.g. Library/272/setStewart14_5/problem_3.pg repeated 8 times) all with 8 parts.  In the first set do 1 part correct and in the second set do one part correct in each problem.  On the problem check the score for the one part and the recorded score. On the problem set page check the score. Check the score in the "grades" section. Finally score the set and check the score on the resulting csv file.  All should report 13% or .13.  Next check the set with 8 problems.  Even though each problem has a reported rounded score of .13, the total should be 1.00

Note that there are still issues with the statistics page but (1) this page is only seen by profs and rounding issues in scores here will get absorbed when there is a lot of data and (2) this page has other issues so we can address the rounding issues at a later time.