Group Error status - no tests

Update group status to ERROR if all the jobs failed. If any one of the job succeeded change it to ACTIVE. This way groups with invalid launch configuration are marked as ERROR. The status change does not impact policies execution. They will be executed based on webhook or schedule even if group status is ERROR. Its just that group will go back to ACTIVE if even a single execution This will help in:
- Metrics will filter groups with ERROR to give more accurate graph
- Feedback to the user about invalid config when cloud feeds has autoscale events
Right now the status can remain only in DB and used by metrics. It can be given out in API and Reach when cloud feeds has autoscale events. 

I've put up this PR to start discussion about this. This will be even more important with convergence. Not written any tests. Will write them once everyone is fine with this. I could've created an issue to discuss this but wrote the code instead as 1) felt like coding and 2) things move faster with code :).
I'm guessing this warrants a `NamedConstant` in `otter.constants`.