Fix serialization issues

[DavidLeoni]

There are many of them, and cause the Can't reconstruct operation and failures to load project (which is still saved sometimes, even with auto-save turned off)

At least they are shown in server logs.

[DavidLeoni]

Fixed some issues and merged them in dev-0.3 so at least enrichment re-apply should work, but there is still this error that can cause troubles:

09:03:2016:16:59:53.533 [Thread-46] ERROR project_utilities - Failed to load data.zip during project loading.

  rethrowed exception message: com.google.refine.model.Cell cannot be cast to java.io.Serializable
 Stacktrace: 

09:03:2016:16:59:53.561 [qtp1814546962-41] INFO  refine - request.getPathInfo() = /command/core/get-history
09:03:2016:16:59:53.561 [qtp1814546962-41] INFO  refine - GET /command/core/get-history
09:03:2016:16:59:53.561 [qtp1814546962-41] INFO  refine - Performing command.doGet()