* basic histogram thread using non-arangod threading ... soon to change.
* Add --latency flag. start histogram thread if set.
* convert quick_hist to use arangodb thread and condition objects
* move histogram object to be within ImportStatistics structure.
* update the thread shutdown to 1. work and 2. post last data
* add text that values are in microseconds to command line help.
* CHANGELOG note for new import latency option
* quick_hist.h rename to QuickHistogram.h
* update include file name to QuickHistogram.h
* update variable names to match coding standard
* a couple more code standard changes. try/catch around push_back