Correcting the getEnergyUsagebyDay's function. Now return in normal
household unit (kWh).
Thing need to be re-touched are:
1. addParam of interval end Day, instead of 'limit's value' as it is
now.
2. It seems 'getEnergyMeasurements()' is re-called all the time. I
couldn't find where it is possibly cause this issue, but at the
RoonServiceTest class. I personally don't think where this issue is
occur.
3. The DB design for policy model a bit complicated. I draw only on my
paper. So I can't attach to gether with this commit as e-file.