update node pressure calculation and refactor a function to write node mass flow
update node pressure calculation and refactor a function to write node mass flow

- line 331-336: correct sign convention for node pressure calculation
- line 1350/1410: seperate `write_substations_to_node_df` function for
temperature and pressure calculation

architecture-building-systems/CEAforArcGIS,architecture-building-systems/CEAforArcGIS