Reporters updates

* simplified the use of line charts/bar charts
* refactored some iterationName/Value trouble
* changed API for adding results (hey, @alanfx, check out!)
* added reporter storing serialized data
** now you can run the benchmark just once and then use report.sh to generate whatever report you want out of it ** this should be useful both for debugging reporters and when you want to merge/remove some results from the report - just paste all the reports to one directory and generate the report

Realizing I've seen this pattern several times, it might be useful to introduce Utils.concat method taking Collection<String> as a parameter (currently there's one with varargs param).