Let Users Follow All Bills an Organization Follows

## Problem

Users wants to follow all bills the organizations they care about care about. Organizations want to be able to help their members keep track of the bills they've identified as important.

To that end, we want to add a way for users to easily follow all bills that a given Organization follows.

Paths this can take:
- Simple Button that users can click to follow (or unfollow) all bills currently followed by an org
- Automatic Transitive Dependency - By following an org, you also automatically follow all of the bills that organization follows
- Optional Transitive Dependency - When following an org, there is more than a binary "Follow"/"Don't Follow" option. Now, there are multiple settings: "Follow Testimony / Don't Follow Testimony" for the current behavior and "Follow Tracked Bills / Don't Follow Tracked Bills" for this new desired behavior.

## Success Criteria
- [ ] TBD

## Open Questions
* Should the list of bills be dynamic?
* e.g. Org "Pythagorean Pizza Society" follows bills 1, 2, and 3. Then, User ABC follows the Org "Pythagorean Pizza Society" with this feature. If the Org changes the list of bills they follow - say by following Bill 4 and unfollowing Bill 2 - what should User ABC now be tracking: The original set of bills when they signed up (`1, 2, 3`) or the current set of bills (`1, 3, 4`)?
* We've broached the topic of bill "playlists" before - where orgs have wanted to set up groups of bills for users to follow. Is this just a specific application of that topic?