Add filters for contribution graph

[flodolo]

Reference: specs

To implement the contribution graph, we need to be able to link to new filtered views:

• Reviews performed by user
• Reviews received by user

Once implemented, the latter should also be used for review notifications.

[mathjazz]

There are 3 types of activities tracked by the Contribution Graph:

1. Submissions: translations submitted by the user.
2. Reviews performed: reviews performed by the user.
3. Reviews received: reviews from other users, performed on suggestions submitted by the user.

We can filter these actions using the following filters:

1. author + time
2. review_author + review_time
3. author + review_time

Which means we need 2 new filters:

1. review_author
2. review_time