Calculation in instance properties

[jack-ii]

In Photoshop, Blender, etc., values ​​in fields for position, size, etc. can be added, divided, ... This would also be very useful in GD, e.g. to quickly position object instances with the same distance.

I know a contributor tried this a few years ago, but the solution wasn't that good and it was canceled. Since then we have AlexandreS & ClementPasteau on board and it might be worth another try :)

• [ ] Add value calculation for the properties panel (X, Y, W, H, Rotation)