Kw measurements and cost calculation

[martinberlin]

In this issue we can discuss, plan, and mention it in the commits where the formula is modified.

• DS3231 second tick calculation
• PCF8563 second tick calculation. This one will require additional libraries modified for ESP-IDF. Pending to be merged in master

Main task will be to build a simple CPP main program that counts how much seconds the switch is on and based on this inputs:

#define DEVICE_CONSUMPTION_WATTS 100
double  DEVICE_KW_HOUR_COST    = 0.4;