Documentation: To get Timeseries working in grafana exactly one column should have the name timestamp

[larswitte]

Grafana needs one column of type time to know how to display time series data. Otherwise it will display the error ``
The united manufacturing hub datasource is configured to only change the column type of the column with columnName timestamp! This needs to be documented in the documentation, because it is not obvious.

united-manufacturing-hub-datasource/src/DataSource.js

Lines 125 to 130 in 7f7a180

	if (columnName === 'timestamp') {
	frame.addField({
	name: columnName,
	type: FieldType.time,
	values: datapoints[queryIndex][columnIndex],
	});