Datastore limitations

[AlexandreOndet]

Currently the limitations we have related to the google datastore system are two things:

• Pagination: The cursor can only go forward, so if we click one page back we to go to page one. More info. This limitation is okay for now as we only use that in the admin section, but if we want to use it for rankings directly, I maybe have an idea to fix it artificially by building an history of cursors.
• Filtering: Originally filtering only supported exact match of full words. I improved it to include partial match but it only works
  with the start of the string. Adding more tricks could maybe improve that but I'm not sure.