Updates to energy accounting work

The patch contains:
1) general code cleanup
2) documentation concerning the energy framework
3) fix for sstat header/data mismatch problem
4) changes on the rapl plugin to print the average power consumption between 2 measurements
in place of an instantaneous value:  this is printed for CurrentWatts value of "scontrol show node"
5)the memory leak that Moe located on cpu frequency code

we are currently working on the following :
- the requested frequency as described by Martin
- rapl fine grain measurements (socket level)
- the ipmi plugin based on freeipmi

and we hope to have them either during your 2.5.0.rc1 testing period or for the 2.5.1