User friendly error: item is not allowed in folder

It's a result of spec validation logic for items that are not inline with spec. In this case the package name was different than the filename prefix:

```
item [azure-ffe22180-ec1c-11e9-90ec-112a988266d5.json] is not allowed in folder [/mnt/c/work/integrations/packages/azure_logs/kibana/visualization]
```

Expected:

Error message should at least suggest the potential fix.