Add / Replace Image Stack doesn't allow .fits files

[MikeSullivan7]

Summary

Loading any extra files through the "Add / Replace Image Stack" dialog does not allow the selection of .fits files

Steps To Reproduce

Open MI and load data, then right click the data stack on the tree on the left and click "Add / Replace Stack". Clicking the "Choose File" button only allows .tif and .tiff files to be selected.

Expected Behaviour

The "Add / Replace Stack" should be able to load the same file types as the main Load Dataset file dialog.

Current Behaviour

Only .tif and .tiff files can be loaded though the "Add / Replace Stack" file dialog