Start of 2015 data

The following notes are from Elsa logbook:

> 30.1.15 er configfilen med de rigtige korrektionskonstanter til pyranometre sat i drift.
> Programmet læser ikke configfilen. Det problem er rettet af Lars Kokholm 18/2 2015.
> Alle de gamle korrektionsfaktorer er ikke i configfilen endnu. Har ikke kunne lokalisrer flyttekassen med HLU's gamle mapper :-(
>11/3-15 kl 15:04:50: korrektionsfaktorerne for globalstrålingen (CM11) og diffus stråling på vandret med skyggering (CM11) er ført ind i config-filen og cRIO er genstartet.

These notes indicate that data is first good from data might first be good from February 18 and GHI from March 11th of 2015.

Edit: I am not sure there are measurements prior to these dates.~~However, there are sensible measurements prior to this.~~

Review the 2015 measurements alongside the configuration-file history and Elsa's logbook notes, focusing on the February 18 and March 11 dates. Determine whether measurements before those dates are valid and document the earliest reliable date for the data and for GHI.

Written by the indexing model from the issue text.