Move CSV scoring to the correct tables #1530

@jbau  please.


Removes appropriate:
ExamRecordScore
ExamRecordScoreField
ExamRecordScoreFieldChoice

Creates new:
ExamRecordScore
ExamRecordScoreField

Updates score in:
ExamRecord
ExamScore

Also, I replaced the colons in the export file names with dashes as
colons are not good in Windows file names.

Also, fixed blank line problem on grade export.