Group linkage error info in plugin

Currently it looks something like this:

mockito-core-2.18.0.jar (2 errors):
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice$ForReadObject
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice$ForEquals
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice$SerializableRealMethodCall
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher is not found, referenced from org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice$ForHashCode
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher.get is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice$ForReadObject
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher.get is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice$ForEquals
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher.isMock is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice$ForEquals
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher.get is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice$SerializableRealMethodCall
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher.set is not found, referenced from org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher. is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher.get is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher.isMocked is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher.isOverridden is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher.handle is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher.get is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice$ForHashCode
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher.isMock is not found, referenced from org.mockito.internal.creation.bytebuddy.MockMethodAdvice$ForHashCode

1. We should organize this a little better when the same missing method is found with multiple sources. E.g.

mockito-core-2.18.0.jar (2 errors):
org.mockito.internal.creation.bytebuddy.MockMethodDispatcher is not found, referenced from
* org.mockito.internal.creation.bytebuddy.MockMethodAdvice$ForReadObject
* org.mockito.internal.creation.bytebuddy.MockMethodAdvice$ForEquals
* org.mockito.internal.creation.bytebuddy.MockMethodAdvice$SerializableRealMethodCall
* org.mockito.internal.creation.bytebuddy.InlineBytecodeGenerator
* org.mockito.internal.creation.bytebuddy.MockMethodAdvice
*org.mockito.internal.creation.bytebuddy.MockMethodAdvice$ForHashCode

2. Furthermore, when an entire class is not found, as here, we don't need to bother printing individual missing method and missing field errors from that class.