Rewrite electricity-logger to use an sqlite3 database

docs/SOLAR_API.md

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+# The solar-server REST API
+
+This project depends on the `pistache` HTTP framework, see their [website](http://pistache.io/) for more info.
+
+## Endpoints
+All endpoints respond in JSON. Examples can be found in the Examples section. Dates are always in ISO format, meaning they take the shape of `year-month-day` with leading zeroes for month and day. Example: `2019-01-11` is the eleventh day of January, 2019.
+
+- `/day?start=[yyyy-MM-dd]` This tells the server what date to serve all the collected records from the specified day.
+- `/day?start=[yyyy-MM-dd]&stop=[yyyy-MM-dd]` This tells the server what date to serve the highest recorded kilowatt hour collected for each day in the specified date range. Stop date is inclusive.
+- `/month?&start=[yyyy-mm]&stop=[yyyy-mm]` This returns the total kilowatthours generated for a given month. The stop month is inclusive.
+
+## Example Response
+All times are always in UTC. For these examples the current date is 25 December, 2019.
+
+### /day?start=2019-02-15
+Will give you as many objects as there are recorded values for the 15th of Febuary, 2019. Ordered from earliest to latest.
+```json
+[
+	{
+		"time": 1550226776,
+		"watt": 1456,
+		"kwh": 14.53
+	},
+	{
+		"time": 1550226834,
+		"watt": 1456,
+		"kwh": 14.54
+	},
+	...
+]
+```
+
+### /month?start=2019-06&stop=2019-06
+Will give you a total kilowatt hours generated for the month July, 2019. The time component is the first day of the month at 00:00 (midnight) UTC. For multiple months the result is ordered earliest to latest.
+```json
+[
+	{
+		"time": 1559347200,
+		"watt": 0,
+		"kwh": 451.64
+	}
+]