Custom template paths for Modelica output

[PGorzalka]

What is the problem?

• The current implementation restricts templates to files located in pre-defined paths within TEASER's folder structure

Why do we want to solve it?

• For custom applications, it would be nice to switch between different Multizone and ThermalZone templates

How do we want to solve it?

• Add an optional parameter to the export_aixlib function that specifies a path to a template on the local hard drive

Additional context

This issue is related to a case-specific application of AixLib (ROM) and TEASER which also includes issue #1080 in AixLib (others may follow after email consultations)

[PGorzalka]

Discussion with @DaJansenGit (see here) lead to the envisaged contributions of

• non-constant soil temperature
• interzonal heat exchange (TEASER and AixLib)
• custom template paths for Modelica output in TEASER as described in this issue
• a new possibility to estimate interior wall area (relates to #474 )