Driver data generation based on FLUXNET2015

[stineb]

Instead of subsetting from FDK, download daily file from FLUXNET2015, and generate driver from that. Code From FDK can be used (file fdk_format_drivers.R).

[fabern]

This should be addressed in #299

Note that, FluxDataKit (FDK) made use of

• hourly values to derive: vpd, tmin, tmax
• further data sources for ccov (CRU data) and fapar (MODIS MCD15A2H)

Thus, these parts of FDK would need to be reproduced in the rsofun code when moving driver generation within rsofun to Fluxnet (FLX) + MODIS + CRU.

Furthermore, note that data download must be done manually due to login restrictions of FLX.

[fabern]

Because of the above difficulties this issue is not followed up. Example data continues to be based on FluxDataKit.