Fulcro 2.0: Support auto-error handling for recoverable network errors

[awkay]

The new history system will enable a cool kind of error handling that will simplify apps. It will be opt-in, since there are server requirements you must agree that you meet:

• Add code to network layer for auto-retry
• Add a way for the application to see the back-log depth
• Add code to traverse history and affect retries

[awkay]

I'm clearing this from the 2.0 milestone, and deferring it. Most of what we need is there, but I'll be happy if we can get this result by year end. I don't want to defer 2.0 just for this.

[awkay]

This is simply not something I'm going to code until someone actually wants it. Too many other things to do, and unhappy path handling just isn't where people's heads are.