Deprecate and comment the MessageInterface simple constructor
Fix indentation and import orders
Group SimpleJsonInterfaceMarshallers

Instead of a big if/else for each interface type, use a Map to
associate a SentryInterface to a SimpleJSonInterfaceMarshaller.
Add a Marshaller (incomplete) for HttpInterface
Reduce SimpleJsonMarshallers names and visibility

Instead of using the complete name "SimpleJsonXxxInterfaceMarshaller"
use the shorthand "XxxMarshaller".
Those marshallers should only be accessed from the SimpleJson
marshaller thus the visibility is reduced to "package" when possible.
Avoid initialisers when a Constructor can be used