Add tests for kotlin interop

[malczuuu]

For better Kotlin interop, it would be good to allow returning proper deserialization/binding errors, while trying to use non-nullable fields. Because simple (Int, Long etc.) non-nullable fields are represented in bytecode as primitives, following exceptions were identified at the moment.

• Jackson will throw KotlinInvalidNullException (subclass of InvalidNullException) if trying to deserialize to non-nullable field.
• Jackson will throw MismatchedInputException if trying to use invalid value for a primitive (like a "text" for an int).

Decided to use Type mismatch error instead of Validation failed as it is better suited and in fact does not involve validation - this is a deserialization failure.

Note that all of these can also occur in normal Java application, so the benefits of this change are not limited to Kotlin apps only.

Edit: changes were applied to #93, so primitive deserialization errors are fixed in 1.2.x version as well. This PR includes only tests for Kotlin interop.