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.
deactivated console.log('rov.lift:' + rov.lift)

deactivated console.log('rov.lift:' + rov.lift), because it is not uniformly used here. Would be better to either log every movement or none in console.
sorted comments

sorted comments the way the functions are called
updated voltage levels

updated voltage levels for 7v minimum and 10v max, taking into consideration voltage drops from diodes.
reverted last change

reverted last change to uncommented version
added missing comma

added missing comma inbetween the batteries
Merge pull request #311 from thunderstorm99/master

Added LiFePO4 batteries & set as default