Implement Profiles in menu only

I have implemented the same menu as scene collections. 

The profile menu now has:
- New
- Duplicate
- Rename
- Remove
- Import
- Export

It functions the same but for profiles. 

I have removed the Add/Rename/Remove from settings general. I have left
the profile combo box because it is still useful when a user wants to
switch to a different profile while in settings.