Run abiotic components of the Virtual Ecosystem on daily time step and return monthly values

[vgro]

Is your feature request related to a problem? Please describe.
A lot of the microclimate and hydrology needs to be represented at a (sub-)daily time step, which is shorter than the current monthly model time step. The abiotic_simple model can return monthly means, so this is not so much of an issue.

Describe the solution you'd like
The hydrology model has a hacky solution at the moment: the monthly rainfall and evapotranspiration (previous time step) are divided by 30, the model loops over 30 days, and return monthly means/sums, whatever is appropriate for a variable. Note that this rather hacky way does not account for feedback with other model parts.

The mechanistic abiotic model is currently not running but will need something similar to work properly.

Describe the solution you'd like
The first step could be to implement a similar loop in the abiotic model and return monthly representative values.

Describe alternatives you've considered
An alternative could be to run the microclimate for one representative day per month. This would make it possible to represent all processes dynamically and get a diurnal cycle including min and max temperatures, i.e. extreme values. This would also require some changes to the handling of time in the data object.