Dashboard should display a clear error page when initialization process is failed

[sleshchenko]

Is your enhancement related to a problem? Please describe.

When dashboard fails to initialize, the blank page is displayed.

Describe the solution you'd like

We need to wrap UD pages with special components called error boundaries so they will catch unhandled JS errors in their child component tree and display a fallback UI.

To reproduce it, just run Dashboard next locally and configure it to use non-existing Che Server, like yarn start --env.server=https://8.8.8.8.nip.io