Minor jfuzz improvements.

Rationale:
Added simple class hierarchy to jfuzz output (still rather
rudimentary, but at least covers all method invocation kinds).
Also cleaned up the array dimensions logic.
Finally, increased granularity of time-based seeding.

Test: ./tools/jfuzz/run_jfuzz_test.py
Change-Id: I6582a75e5be593ba56146e1cd56f801e85f051c5