Improve runtime error detection for userapps

[bodom0015]

When an app encounters an error at startup, we try to detect this and write the Error status back to the database.

When an app encounters an error at runtime, we should do better at detecting this case as well - the container will go into CrashLoopBackoff and should write the Error status back to the database

Considerations:

• The UI is only polling for app status when the app is starting or stopping (every X seconds), or if the user manually refreshes the page