Change component position settings (x, y) using mouse

[tassaron]

The user should be able to click/drag the preview window to move where components draw.

The Title Text component has a "center text" button. This could be a good addition to other components, namely the Image one.

Components aside from Title Text and Image tend to cover the entire frame, so conveniently setting the positions of those is a lower priority. But maybe it could be implemented if the UI isn't confusing.

To-do list

• Add "center image" button to Image component
• Allow clicking preview window to set x, y of Image component
• Allow clicking preview window to set x, y of Title Text component
• Add test to ensure that clicking preview window changes x and y