Added map_generateRRDFile() for #6

Next step, add some code on maps_statify(), test and go!
Saving per maps data into RRD files seems ok

need few testing ;)
DS name can't have more than 19 chars
Add option to disable historical data for maps

Disabled by default
Merge pull request #7 from blapecool/dev-mapsUpdate

Introducing Historica data for each maps.