ForJoinPool for batchUpdate investigation

[g4s8]

Now, the Rpm.batchUpdate() method runs in parallel for each package file to update on RX IO-scheduler. Let's investigate if it's possible to schedule package parsing tasks on ForkJoinPool maybe with RecursiveTask where package parsing task can be self-estimated and decomposed to subtasks. First we need to create some benchmarks to analyze the speed of current butchUpdate() version and compare it with a new solution.