Reactive State

[ErikDakoda]

• Added a new mechanism for storing global state in Apollo Client 3 reactive variables
• Implemented supporting functions in reactive-state.js
• There is a pull request for the documentation: https://github.com/VulcanJS/vulcan-docs/pull/163
• Another PR forthcoming, "Flash messages in reactive state" depends on this

[ErikDakoda]

@eric-burel Thank you for your feedback on my last pull request. Based on your suggestions I made a few changes that I think improved and simplified the implementation of this feature:

• I decided to keep the global state registry - primarily because I wanted to keep the ability to reset all reactive state when the user logs out (or any time the Apollo client store is reset)
• I updated the documentation to encourage the use of import statements instead of relying on the global state registry
• I decided to jettison immutability-helper for a more intuitive way to mutate object state - it now works very similarly to React's setState()
• I decided to also jettison useReactiveState and withReactiveState and the documentation shows how to import and use reactive state in a component

[eric-burel]

Sounds great to me! The code feels simplified indeed that's great.

[eric-burel]

@ErikDakoda I'll let you merge yourself if you want to do a last check