feat: namespaced keychain

[johnny243]

Related: standardnotes/snjs#13

[arielsvg]

https://github.com/standardnotes/web/blob/004-namespaced-keychain/app/assets/javascripts/ui_models/application.ts#L59
The WebApplication class still defines the namespace as an empty string. Should it be injected instead?
Also how will the application get the keychainValue from an 003 installation?
I guess if namespace stays an empty string this works with 003 installations but then doesn't achieve namespacing completely.

[moughxyz]

I suppose it might make sense to think about how multiple application namespaces would look like. We will need to persist namespaces in localStorage as a top-level key I think (nonwrapped). Then each new application instance would determine its namespace based on the length of existing namespaces.

Something like:

/** Before creating an application */
const namespaces = localStorage.get("namespaces") || [];
const namespace = `application-${namepaces.length}`;

const application = new Application(..., namespace, ...);

[arielsvg]

I suppose we can address this when we get to actually run multiple applications at once. I just thought that was the intent of the feature.

[arielsvg]

Please also update the snjs dependency, I'm assuming that's why the type check is failing :)