Improve editor

- Added Shortcut to Create Quads in Mouse position
- Add Image preview in "Add Image Dialog"
- Change points color to selected quad
- Highlight quad when moving points
- Texture preview and size selector in Layers List
- Added "View" & "Brush Mode" Menus in MenuBar
- Added "Addition" mode to bursh (Omit index 0 when DrawBrush)
- Other stuff