Update Review Data Parsing Scripts

[shiva-menta]

While uploading the review data from semesters 2024A/B, I ran into a few errors due to some new formatting. The changes are summarized below:

• Summary Rows can have some null values for keys such as RWORKREQUIRED. When we create ReviewBit objects, we want to ensure that there is at least some data present that we are saving. The assumption is that if we are not given a value for these fields in the summary dump, there are no values to be saved.
• Ratings Rows also now have some null values for keys. Our previously logic was checking if val is None, but our parser is not catching these values, so we want to also check for the string "null".
• Date information from this dump came in a new format, DD-MON-RR, which required parser support. The RR year format isn't supported directly through Python's datetime module, so we added an additional function to find the four digit year it corresponds with. More information on this conversion here.

[el-agua]

lgtm