Added LiFePO4 batteries & set as default

Added LiFePO4 batteries and set them as default. Voltages taken from this site: http://www.powerstream.com/LLLF.htm
Lower boundary set a little higher (2.2V rather than 2.0V) in order to have a safety gap.

Also deactivated console logging of the rov.lift function in tankcontrol.
What's the reason to comment this line out? This has nothing to do with the Battery change.
Same is true for the rovpilot.js file above.

Could you revert these change and do another commit to your branch?