User feedback before Update files

[ace-dent]

When changing core lib files (splash screen, etc.) via the 'Filesystem' it is too easy to click UPDATE and overwriting the changes made. Suggest:

• Renaming 'Update' to 'Restore' (for clarity).
• Add a Yes / No prompt window, e.g. "This will restore all core library files. Continue?".

[ghost]

I added a warning when pressing that button: 430a4b2

As for renaming it, I'm not sure what a good name is since that button is turned red to indicate the files need updated. That might still work if it was called 'Restore'