Add save state support

[JaCzekanski]

• [x] Compatibility with existing formats/write custom one?
• [x] Find binary serialization library (JSON isn't a perfect choice here: binary JSON, Cereal, ProtoBuf, something else?)
• [x] Serialize / deserialize state of CPU and devices
• [x] Compress with Zlib (already in the dependencies)

[JaCzekanski]

Cereal was chosen - it is quick enough for this purpose and makes the implementation of serialization very simple - almost all types used in the codebase are supported out of the box. Making class serializable is just a matter of adding a single templated method which references fields to be saved.