Improves diagnostic output.

* toString() of Schema Rule Commands return the actual Schema Rule,
  rather than the DynamicRecord that is used to represent it. This
  improves the output of DumpLogicalLog.
* messages.log now always contain the revision (git hash) of the Kernel.
* Exceptions from RecoveringIndexProxy includes information about what
  the index is that is recovering (using the index descriptor).

+ some minor formatting fixes in IdGeneratorImpl.
Test cases for Unique Index recovery issue.

Recovery fails (with "cannot await recovering index") when recovering a
store where the active log both creates and drops the index in question.
Don't activate indexes during recovery.

The correctness of this is based on the assumption that there are other
processes (already in place) to make sure that the indexes are activated
post-recovery.