This script was broken on Debian Jessie (and probably
all other Debian-based distros, including Ubuntu).
This commit removes the hard-coding of paths and uses
$PATH per normal bash practice, and should work on a
wider range of shell variants.
* new code for better matching, snmp-extend compliance
* removed unused vars
* extra fixes
* removed the need of tmp file
* removed charge_low, deemed useless by user
* removed values that are not plottable
* readded ds