Code: Implement binary serialization and deserialization for model classes

[smarkwal]

Implement a binary serialization and deserialization for all model classes (JarFile, ClassDef, FieldDef, MethodDef, ClassRef, etc.). Use it to store and load information about JAR files to/from a cache, using the JAR file's checksum and/or coordinates as key. Such a cache could dramatically speed up the scanning phase.

Open question:
How can we detect relevant changes to model classes so that JarHC can invalidate its cache?

Similar to #93.