Added functionaility: simultanously loading multiple pipelines / recover scence in camera viewport if lost

This MR adds 2 features to Met.3D.

(a) ability to select multiple pipelines at once when loading pipelines in Met.3D. This change moves the loading of the pipeline settings out of the pipeline settings GUI, and instead the GUI is only used to actually edit the pipeline. The open file dialog was moved to the main windows, as that is the window that opens the dialog. The loaded pipeline settings then are passed to pipeline settings GUI objects to edit them.

(b) a new button for camera manipulation in the scene settings tab within the system control panel. This button allows the user to move the camera to a location where it views the whole scene in its viewport, while leaving the camera rotation the way it is.