get_telemetry_data: Get a vector of telemetry data
In kdayday/ppnwp: Post-Process Numerical Weather Prediction ensembles

Selects either Maxar or NSRDB format and loads data vector Time-point selection is a consecutive sequence If the final forecast run(s) have a horizon that extends past the final valid telemetry point, the telemetry is buffered with NA's for those time points.

1	get_telemetry_data(fname, site, metadata, date_start, date_last_issue, ...)

`fname`	file name
`site`	Site index
`metadata`	Metadata list including date end, temporal parameters, time-steps per day, rolling or not, etc.
`date_start`	A lubridate: Start date of data to load
`date_last_issue`	A lubridate: Last issue time in the ensemble