[gpm] Using HAL: reporting.low and reporting.warning

[Jaap Haitsma <jaap haitsma org>]

Hi Richard,

My batteries have as properties in HAL a reporting.low and 
reporting.warning (also charge_level.low and charge_level.warning and 
these have the same number so I guess they are the same thing)

Can't we use these properties instead of the sliders? Or are these 
properties not present for all type of batteries?

Jaap