* optimized ses and added des
* added coefficient of variation
* fix bug identified by @vlvkobal: use all available points when resampling is required and the timeframe is not enough for a single point
* modularized exporters
* modularized API data queries
* optimized queries
* modularized API data reduction methods
* modularized api queries
* added new directories in makefiles
* added median db query
* moved all RRDR_GROUPING related to query.h
* added stddev query
* operational median and stddev
* working simple exponential smoothing
* too complex to do it right
* fixed ses
* fixed ses
* rewrote query engine
* fix double-exponential-smoothing
* cleanup
* fixed bug identified by @vlvkobal at rrdset_first_slot()
* enable freeipmi on systems with libipmimonitoring; #4440
