Merge pull request #1865 from ceeaspb/master

Recorder: fix for exception in export proxy not shutdown
Move some code out of FileHelper that's purely chart related
Move some constants that are only related to SeparatedValuesParser
Refactor: merge IOHelper and FileHelper into IO
minor clean up
clean up
Refactor Recorder's CommandLineConstants
Third field of ErrorStats was being used inconsistently - as a percentage in some places, and a total in others (leading error rates over 100% in "Global Information")
Merge pull request #1872 from jamespic/percentage-fix

Percentage/Total confusion
New cheatsheet + docs fixs
Merge pull request #1873 from excilys/cheatSheet

Doc: New cheatsheet + docs fixs
Use HdrHistogram for computing live metrics
Use a fixed buffer of 1s rather than 10% for sizing the metrics histogram
Merge pull request #1875 from nremond/hdr_histo

Metrics: Use HdrHistogram for computing live metrics, close #1868
Fix proxy port command line option
Refactor config constants to mimic conf structure
Merge pull request #1877 from excilys/recorder-mimic-config-structure

Recorder : Refactor configuration constants to mimic config structure