Removed lock around for SimpleLogger.DATE_FORMATTER by using ThreadLocal<DateFormat>

- for relative time new anonymous inner class based on DateFormat is created
- made SimpleLogger.START_TIME final
- unit tests for SimpleLogger.DATE_FORMATTER
- added jmockit 1.12 dependency
- SimpleLogger u-benchmark using jmh
  http://openjdk.java.net/projects/code-tools/jmh/ in separated module

Results of benchmark
With LocalThread
Benchmark                                      Mode  Samples       Score      Error  Units
o.s.i.SimpleLoggerBenchmark.eightThreads      thrpt       20  291713.679 ± 2090.442  ops/s
o.s.i.SimpleLoggerBenchmark.fourThreads       thrpt       20  291552.450 ± 1771.590  ops/s
o.s.i.SimpleLoggerBenchmark.oneThread         thrpt       20  548539.921 ± 3197.140  ops/s
o.s.i.SimpleLoggerBenchmark.sixteenThreads    thrpt       20  281860.846 ± 3172.071  ops/s
o.s.i.SimpleLoggerBenchmark.twoThreads        thrpt       20  290422.132 ± 2213.392  ops/s

With synchronized block
Benchmark                                      Mode  Samples       Score       Error  Units
o.s.i.SimpleLoggerBenchmark.eightThreads      thrpt       20  251927.856 ±  4606.081  ops/s
o.s.i.SimpleLoggerBenchmark.fourThreads       thrpt       20  289278.497 ±  1899.424  ops/s
o.s.i.SimpleLoggerBenchmark.oneThread         thrpt       20  550569.540 ±  4470.577  ops/s
o.s.i.SimpleLoggerBenchmark.sixteenThreads    thrpt       20  275318.387 ±  3156.346  ops/s
o.s.i.SimpleLoggerBenchmark.twoThreads        thrpt       20  295816.125 ± 24218.907  ops/s