Improve engine extensions

[Reco1I]

• Requires Corrections after 1.8.1 release #474

Relevant changes

• Implemented relativeSizeAxes to ExtendedEntity which allows to set relative values w.r.t its parent for width and height in a range of [0, 1].
• Implemented relativePositionAxes to ExtendedEntity which accomplish the same behavior than relativeSizeAxes but for position coordinates.
• ExtendedEntity now handles properly input and collision when origin is not at 0,0.
• Added ability to clip children entities on a ExtendedEntity.
• Introduced Triangle shape.
• Introduced ExtendedText and TextSprite (both are different, TextSprite has more advanced capabilities compared to ExtendedText but it is less efficient)
• Vertex buffers now updates in the draw thread rather than the update thread, this lead to concurrency issue in some edge cases so it is safer to change the vertex buffers in draw thread.
• ExtendedEntity's Origin and anchor properties now uses Vector2 class (Rian's package).
• rotationCenter and scaleCenter are now back customizable.