POST/PUT breaks for Byte, Short and BigInteger types

[andrus]

We are missing converters for Byte, Short and BigInteger types, so when Java objects have properties of those types, exceptions are thrown.

io.agrest.jaxrs2.provider.JaxrsAgExceptionMapper - 500 Internal Server Error (Exception processing Agrest 
request) [cause: class java.lang.Integer cannot be cast to class java.lang.Byte (java.lang.Integer and 
java.lang.Byte are in module java.base of loader 'bootstrap')]

io.agrest.jaxrs2.provider.JaxrsAgExceptionMapper - 500 Internal Server Error (Exception processing Agrest 
request) [cause: class java.lang.Integer cannot be cast to class java.lang.Short (java.lang.Integer and 
java.lang.Short are in module java.base of loader 'bootstrap')]

io.agrest.jaxrs2.provider.JaxrsAgExceptionMapper - 500 Internal Server Error (Exception processing Agrest 
request) [cause: Failed to instantiate type: java.math.BigInteger]