add 'massflows per tech' to massflow_stats

[spuhlerd]

add everything to massflow_stats (but do not export to df)

For each tech give info on
transferred per output/recovered
three losses
mean, sd, quantiles?

Maybe later if needed for UX: make function to represent flows within a system (to make sankey diagram)

[spuhlerd]

The risk is to make system properties too heavy. Two options:

• 1. calculate mass flows live using the transfer coefficinets saved per tech. For this, we would need a function that calls Santiago and returns the massflows per tech. E.g. massflows_per_tech(tech, inflows) - the problem is, that this means we would need to save for each system the massflows in Santiago for inflow=1 and then scale, because the inflow of the tech depends on its position within a system and calculating massflows "live" in the frontend is not possible
• 2. Save the massflow_per_tech and system as separate object e.g. system_massflow[1].properties["nametech"] etc... Based on this e.g. for the uddt contained in system xlz-uuu we could get the massflows by system_massflow["ylz-uuu"].properties["uddt"]["phosphorus"]

You to decide!

[scheidan]

610f615 adds an option techflows to massflow_summary!, see readme. If this is true the individual massflows through every tech are stored iunder properties["massflows"]["tech_flows"].

The default is techflows=false, because if set to true, the exported JSON files are almost 2.5 times larger.

[scheidan]

The comment above links to the wrong commit. This is the right one:
e628419

[spuhlerd]

This needs to be tested and added to bestpractice runfile and WIKI