Add general class for list of timestamped values

Signed-off-by: Tomas Hozza <thozza@gmail.com>
modify Measurement class into MeasurementList class

Signed-off-by: Tomas Hozza <thozza@gmail.com>
Remove unit tests for removed Measurement class

Signed-off-by: Tomas Hozza <thozza@gmail.com>
Add some methods to TimestampedList class and clean up the source

Signed-off-by: Tomas Hozza <thozza@gmail.com>
Add unit tests for TimestampedList class

Signed-off-by: Tomas Hozza <thozza@gmail.com>
Doc cleanup in TimestampedList class

Signed-off-by: Tomas Hozza <thozza@gmail.com>
MeasurementList: Implement specific methods to calculate consumption

Signed-off-by: Tomas Hozza <thozza@gmail.com>
MeasurementList: Add unit tests skeleton

Signed-off-by: Tomas Hozza <thozza@gmail.com>
PriceList: modify class to be derived from TimestampedList

Signed-off-by: Tomas Hozza <thozza@gmail.com>
PriceList: remove unneeded unit tests

Signed-off-by: Tomas Hozza <thozza@gmail.com>
Energy: use MeasurementList

Signed-off-by: Tomas Hozza <thozza@gmail.com>