About window: Added missing import.
Preferences: Item list: Added missing import.
Plugin base: Find extension: Set data in a different way.
Plugin base: Rename extension: Set data in a different way.
Tools: Find files: Added missing imports and fixed syntax.
Tools: Advanced rename: Added missing import and fixed syntax.
Plugins: File list: Fixed method of setting data in column editor.
Plugins: File list: Removed unnecessary variable.
Plugins: Find file extensions: Contents: Fix constructor call.
Plugins: Find file extensions: Fixed constructor call in default.
Plugins: Rename extensions: Commented out style fixes.

These are no longer applicable. Styling is done through CSS.