Add statistic entities

[klaasnicolaas]

By statistics I mean entities that give a day, week, month and year value. Preferably we also put these in a single Statistics dataclass function.

• Gas consumption
• Energy consumption / production (return to net)
• Water consumption
• Solarpanels production

or Solar, Water, Energy dataclasses:

Energy

• Gas production - day (delta)
• Energy consumption - day (delta)
• Energy production - day / return to net (delta)

Water

• Water consumption - day (liters and m3)
• Idem month
• Idem year
• Counted pulses

Solar

• Solar production - day (Counting high and low values)
• Idem month
• Idem year