Bug when loading regions

I tag Juan because I think he uses Start() when loading different regions.

As Nico and me were talking yesterday, it seems Start() takes an index of reference (the -number of- position) of the selected region based on the first file it loads. However, we have seen that the regions (when you make 'ncdump -v region file.nc') sometimes aren't in the same order, because of various reasons (1. You want some regions for some dates and not for others, but another person supposes that all dates have the same regions and actually loads another. 2. The post-processing with earthdiagnostics crashes and you change the order of the regions in the configuration file, etc.). In our case, Juan and I are working in some same experiments, with the same variables and this is potentially dangerous, since I have already suffered it with an experiment in which just me was working.

I don't know how much additional time would take to read the index of each file you want to load, but we have showed that it's not the best option always, even if it saves some time.

Moreover, and as Nico and I talked yesterday, it would be great to have some warning when a specific chunk isn't available for a specific region.

If there are other people working with Start() or the temporal versions of Load(), maybe they would be interested in checking this. (Maybe @rfernand ?).

Best, Rubén.