Colour theme switcher
 - Added dark colour theme for more of the editor
   - General Settings
   - Colours
   - Sprites
   - Text Parser
   - Lip Sync
   - GUIs
   - Inventory Items
   - Dialogs
   - Views
   - Characters
   - Mouse Cursors
   - Fonts
   - Audio
   - Global Variables
   - Rooms
 - Refactored code for Colour Switching and dark theme to folder "AGS.Editor\ColourTheme"