[FMI] Usability improvements
- The dialog for selecting the target folder of an FMU file (export) does provide UI elements for creating folders. Thus, one has to manually navigate to the runtime workspace to create one. This is quite inconvenient.
- The FMU specification editor opens the home folder of the user to select a FMU. The dialog should point to the runtime workspace instead.
- The selected file should be imported to a subfolder of the AF3 project directory and referenced. By that, AF3 projects are quasi self-contained and machine-independent. Another idea could be some FMU importing and restricting the selection dialog to the AF3 runtime workspace. The dialog for the FMU export can serve as an inspiration.
- In line with the item above, only relative paths to the AF3-runtime folder and folders below it shall be allowed to be referenced. Reason: Self-containment and machine-independence.