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.
I thought it might not show up here, it seems i do not yet fully understand github. the reasoning for this to be commented out in general is that the other movements are commented out as well, so if this is not used (which i think it is) it seems like someone forgot to comment this out. If I'm mistaken of course I would undo this step.