Automate the verification of trace output from the XTS crash recovery tests

Currently it is very difficult to verify the trace output from the XTS crash recovery tests. With the current code it is infeasible to run multiple servers as the trace output will span many files making it difficult to establish the correct order in which events occurred.

I think, the following changes will make the test verification automatic and the tests scalable to many participants:

1. Carry out assertions in Byteman as the test progresses. Assertions at Runtime should be more flexible as more info is available.
2. Each participant is concerned only with the correctness of their own participation. This is key to scalability to many participants.
3. Anything that can't be solved by the above is dumped to one trace file per server and is hopefuly simple enough for scriptable post-verification.

I think my idea needs prototyping first to check that it is feasible in practice.