Add statistics for prod107

[sbesson]

This should include vital metrics (# of images) for idr0133 /cc @khaledk2

[sbesson]

As discussed during today's IDR meeting, the last commit updates releases.tsv to append the number of published studies per release.

The corresponding change to the generation scripts (https://github.com/IDR/idr-utils/blob/2facf3da884e22ba578b226019cb206b9b9dae21/scripts/stats.py#L1) is simply

index c35db3e..61b2357 100644
--- a/scripts/releases.py
+++ b/scripts/releases.py
@@ -19,6 +19,7 @@ def create_release_stats(studies_file, release=None, date=None, size=None):
         "Size (TB)",
         "Files (Million)",
         "DB Size (GB)",
+        "Studies",
     ))

     suffixes = studies['Introduced'].apply(lambda x: int(x[4:]))
@@ -43,7 +44,8 @@ def create_release_stats(studies_file, release=None, date=None, size=None):
         int(studies[index]['Planes'].sum()),
         studies[index]['Size (TB)'].sum(),
         studies[index]['# of Files'].sum() / 10 ** 6,
-        size)
+        size,
+        studies[index]['Study'].nunique())
     return(df)