Rainmaker integration

[martinberlin]

Add this device to be paired to the ESP-Rainmaker phone app

• Add 2 input forms: Device watts, Price per kilowatt
• Save the updated values in NVSe
• Make the calculation reset itself every 1st day of the month at 00:00 hours saving previous_month total in NVS
• Design an UX that either will be present below all the time (Or a resume) and that gives extra info with a small button

Rainmaker UX preview:

About time sync:
Rainmaker already does a time sync with NTP. Try to use that instead of reinventing the wheel. Problem:

/** Get printable local time string
 *
 * Get a printable local time string, with information of timezone and Daylight Saving.
 * Eg. "Tue Sep  1 09:04:38 2020 -0400[EDT], DST: Yes"
 * "Tue Sep  1 21:04:04 2020 +0800[CST], DST: No"
 *
 *
 * @param[out] buf Pointer to a pre-allocated buffer into which the time string will
 *                  be populated.
 * @param[in] buf_len Length of the above buffer.
 *
 * @return ESP_OK on success
 * @return error on failure
 */
esp_err_t esp_rmaker_get_local_time_str(char *buf, size_t buf_len);

It looks like it only returns a string butter instead of a time struct.

Another things to save in NVS and retrieve in app_main:
int type
I (292358) esp_rmaker_param: Received params: {"EPD Switch":{"Device Watts":"85"}}

float type
I (387998) esp_rmaker_param: Received params: {"EPD Switch":{"Cost of each KW":"0.46"}}

But this is not only meant to be WiFi driven for the people that do not want that. Also offer to add this stored in the Firmware without being associated to Rainmaker.

[martinberlin]

@goran-mahovlic this is starting to take shape for when the S3 model is sent to fabrication.
To test it you should add any DS3231 cheap module in the same I2C than touch.

The round PCB is also done but that will need to wait until mid or end March, so there is time to review it. First prio for me would be to check that CP2102N cheaper model QFN28 works as expected before finishing S3 prototype