Draft: Xfce list view

Enables built-in configuration of column visibility and ordering.

• Allows registration of columns using a string identifier for later retrieval
• Enables these registered columns to be shown, hidden, and moved
• Provides convenience functions for rendering columns using its string id
• Displays a popup on header right-click to enable GUI configuration
• Provides functions for serializing and restoring column state (e.g., for storing in xfconf)