Better async

[martindstone]

This PR fixes a number of issues related to async behavior:

• fix merge behavior by chunking large requests (API errors on large batches)
• disallow marges that would result in >1000 alerts in an incident
• don't dismiss merge modal until merge is finished, show progress indicator on merge API requests
• move polling from app component interval timers to sagas
• implement oauth token refresh
• add error handling for more API and data structure errors
• add error tracking for more errors
• add auto-reload of app on catastrophic errors
• show log entry polling status, last attempted/completed time and latest log entry time in detailed status overlay

[gsreynolds]

Approved!