add API field indicating widget failures

We run into situations where widgets display an error of some sort due to any number of reasons, usually when datasources are changed or resource group structure is updated.  The point is, there is an error displayed in the widget instead of the data, and the fact that is happening is pure stealth currently, just waiting for an embarrassing moment with clients.  I propose that this meta-issue be reflected in a way it can be detected in advance.  If the API can pull that information, then a check could be setup within LM or via external script.  I just checked our JSON dump of all widgets and nothing like this appears to be in place currently.