Additional import options, deletion improvement, and more

[Julian0555]

Hello! I was hoping to give my two cents on some features that could help improve the StudioSB experience.

Model Import Options

• Merge duplicate vertices
• Remove the objects that are already in the scene

Objects Tab

• Delete objects with the delete key
• Add the option to combine objects
• Show/Hide/Delete all objects
• Select multiple objects at a time (preferably box selection)
• Setting to turn off the deletion warning

[feelingLaserSharp]

Most of these seem to be in now.