Clarify serialization strategy behavior

[henri-tremblay]

So far, Objenesis was behaving differently depending on the instantiator picked. We should

• Describe an accepted default behaviour
• Improve the TCK to test this default

The accepted default is

• Fail if the class isn't serializable
• Call the first non-serializable constructor in the hierarchy otherwise
• No special behaviour for Externalizable classes
• No serializable specific method called (e.g. readResolve, readExternal, readObject, readObjectNoData)