Add feature: forking and saving

[garrettluu]

Closes #28, addresses #27

This PR adds UI elements to fork and save a config. I ran into several issues as I was doing this, stemming from the problem of not being able to get the id of the current config (since that isn't stored in the state anywhere). So I propose a new process for forking:

• Forking is not available until user has saved the current config
  • If config is not saved, we do not have a blob to fork from
• Once the user saves the config, the "fork" button appears
  • Create a new blob or update the current blob and store the id somewhere in the application state
• Once the user forks, we create a newBlob identical to the current blob but with a different id
  • Add newBlob.id to blob.forks[] and make newBlob.forkedFrom point to blob.id (this is done in backend)

~TODO~ done!

• [x] Update REPLState to allow for saving and forking
• [x] Store id in application state, or change the url after saving and get id using extractID
• [x] Coordinate with backend for API endpoints and data
• [x] Allow for viewing of forks
• [x] Test forking with real data

[garrettluu]

Finally added displaying forks! Not sure how much I should style this since the UI and layout are probably gonna change soon.

[garrettluu]

Tested forking with the backend and it seems to work and create new blobs, but I would also like to track the forks of the parent in an array in the blob (this is a backend task @mohammedsahl).

If we start with this blob

{
  "id": "example1",
  "forkedFrom": "",
  "forks": []
}

and we fork it to generate this blob

{
  "id": "example2",
  "forkedFrom": "example1",
  "forks": []
}

the forks array of example1 should contain example2 as an element: "forks": ["example2"]

Currently, the forks array seems to always be empty or null.

[mohammedsahl]

Currently, the forks array seems to always be empty or null.

Okay so this seems to be an issue(?) with async DB updates. If you GET example1 after forking it should have forks : ["example2"]

Edit: It appears that forks: [...] is not part of the res body when GETing a single blob, I'll add that right away

[garrettluu]

Tested with real data from backend and everything seems to work! 😀

[wlawt]

We should also update the docs about how the forking logic works just to clarify.

The current process is:

• Add custom plugin -> save -> share -> copy link -> fork -> paste link that was copied -> click the number

[ianjennings]

./src/components/MainMenu.js
Module not found: Can't resolve './ForkModal' in '/home/ianjennings/Development-Unix/babel-sandbox/src/components'

I don't see this file in my local copy, do you need to commit it?