Ratings: Retain original rating date

Hello,

I like to gather statistics about the number of movies I watch for the first time per months/years. For that I rate every movie I watch, use the Export feature of my ratings list to export it to CSV, and count the number of movies in a given timespan using the "created" column.

However, if I ever decide to re-rate a movie, the value of the "created" column is overwrote with the new date. This completely mess up my statistics because I don't have access anymore to the original date I saw/rated the movie. I should point out that the reason I re-rated a bunch of movies recently was solely to trigger the badge associated to this group of movies (so if you could fix that as well).

So it would be a good idea to be able to access the date of the first time the movie was rated. I noticed that the exported CSV contains a column "modified" which is always empty. It would look sensible to me to use the "created" column to put the date of the first time rated, and "modified" to put the date of the last time rated.

Thank you and continue the great work!