Include model name in "The ModelDefinition instance is not valid. Details: name is not unique."

[bajtos]

Modify the code creating models to include model name in the error mesage printed when an attempt to create a duplicate model is detected.

At the moment, the message says "The ModelDefinition instance is not valid. Details: name is not unique.". This is not enough information to identify the problematic model in the situation when multiple models are being created as part of model discovery.

Loosely related to #354.

[bajtos]

This will be fixed by loopbackio/loopback-datasource-juggler#389

[bajtos]

The fix was released in loopback-datasource-juggler@2.14.0.

@cgole please verify. You need to run npm install loopback-datasource-juggler inside Arc to get the fixed version. If you are using builds from our CI, then please consult @rmg how to get a version that includes the updated juggler.