Update SimpleHouse tutorial using feedback of Modelica Conference

[jelgerjansen]

This issue is to update the SimpleHouse tutorial using feedback from the Modelica Conference. Some feedback I already got during the workshop:

• The documentation of SimpleHouse3 mentions a nominal mass flow rate of 1 kg/m3 instead of 1 kg/s.
• The plots in the documentation uses seconds (mega seconds) on the time axis. Days would be a more suitable unit.

@mwetter @LauraMaier @drehelmns @nytschgeusen please let me know if you have any other feedback, then I'll create a development branch and apply these changes.

[mwetter]

@jelgerjansen : Regarding the plot unit, could you please file an issue on the OpenModelica repository. It would be very convenient to switch between seconds and minutes/hours/days, and also use such a switch in units in the experiment setup window.

[jelgerjansen]

I filed the issue of changing the time unit in OM: OpenModelica/OpenModelica#11382
Once this is integrated, I'll update the reference results and create a pull request.

[jelgerjansen]

Typo is fixed in #1899, time unit will be fixed in the future once this is integrated in OM

[jelgerjansen]

Closed by #1899