#166: Add not equal to DB where filter

- This will match the functionality seen in the Python ICAT version of the WHERE filter, so I can put an example of this operation in the Swagger docs

common/database/filters.py

@@ -71,6 +71,8 @@ def apply_filter(self, query):
 
         if self.operation == "eq":
             query.base_query = query.base_query.filter(field == self.value)
+        elif self.operation == "ne":
+            query.base_query = query.base_query.filter(field != self.value)
         elif self.operation == "like":
             query.base_query = query.base_query.filter(field.like(f"%{self.value}%"))
         elif self.operation == "lt":