Automatic replacement of placeholder statements when generating ddck files from the GUI

[martin-neugebauer]

The newly introduced statements in the form of @type(portName, defaultName), e.g. @temp(hpCondIn, TPiHpCondIn), should be correctly replaced with the connection names from the GUI. This requires the completion of a number of subtasks:

• Ensure meaningful port names in the classes of the GUI objects. (@martin-neugebauer should probably do this)
• Copy an existing example (maybe dualSource, but something else would be better for once) and replace the hydraulic input statements with the new ones featuring the already defined default names and the correct port names as defined in the classes (maybe also a job for @martin-neugebauer)
• Save information about input port connection to json-file to be transferred to pytrnsys for dck-building #241
• Add a button to export "connection.json" #243
• Write a test checking that dck files created with port information from the GUI are correct pytrnsys#101
• Implement function that replaces placeholder statements in template ddck-files with the correct variable names when building dck-file pytrnsys#102
• Introduce new run.config keyword to include connection information from the GUI pytrnsys#103
• Add placeholder statements in relevant files in data\ddcks pytrnsys#106
• Document automatic ddck connection feature pytrnsys_doc#1

[martin-neugebauer]

@zuckerruebe Feel free to extend and adapt

[martin-neugebauer]

@zuckerruebe The first task is fulfilled by #235, but some tests still have to be adapted for the changes I made. Maybe this is something that @PuaYongHao could do on Monday. We also need to deal with #234, a problem which was made worse by the changes I did, but I don't see a way around it. This means we might need some translator that translates diagrams of previous versions to the current one, such that we don't need to redo all diagrams by hand (this wouldn't be popular by many users, I guess.)