Curve editor example app

[Mafo369]

• Please check if the PR fulfills these requirements

• The commit message follows our guidelines
• Tests for the changes have been added (for bug fixes / features)
• Docs have been added / updated (for bug fixes / features)

• What kind of change does this PR introduce? (Bug fix, feature, docs update, ...)
  Add a piecewise cubic Bezier class and a new example app of a curve editor.

• What is the current behavior? (You can also link to an open issue here)
  Not existing.

• Does this PR introduce a breaking change? (What changes might users need to make in their application due to this PR?)
  None.

• Other information:
  This PR is based on the PR [tests] move examples apps to their own directory. #958.
  A getter of the brush radius had to be added to the renderer.

[codecov]

Codecov Report

Merging #964 (0dbb2aa) into release-candidate (a2ab1c7) will decrease coverage by 1.11%.
The diff coverage is 0.00%.

❗ Current head 0dbb2aa differs from pull request most recent head d4314a1. Consider uploading reports for the commit d4314a1 to get more accurate results

@@                  Coverage Diff                  @@
##           release-candidate     #964      +/-   ##
=====================================================
- Coverage              29.35%   28.24%   -1.12%     
=====================================================
  Files                    346      363      +17     
  Lines                  22963    23870     +907     
=====================================================
+ Hits                    6740     6741       +1     
- Misses                 16223    17129     +906     

Impacted Files	Coverage Δ
...rveEditor/BezierUtils/CubicBezierApproximation.hpp	0.00% <0.00%> (ø)
...ples/CurveEditor/BezierUtils/LeastSquareSystem.hpp	0.00% <0.00%> (ø)
examples/CurveEditor/CurveComponent.cpp	0.00% <0.00%> (ø)
examples/CurveEditor/CurveEditor.cpp	0.00% <0.00%> (ø)
examples/CurveEditor/CurveEditor.hpp	0.00% <0.00%> (ø)
examples/CurveEditor/CurveFactory.hpp	0.00% <0.00%> (ø)
examples/CurveEditor/Gui/MainWindow.cpp	0.00% <0.00%> (ø)
examples/CurveEditor/Gui/MainWindow.hpp	0.00% <0.00%> (ø)
examples/CurveEditor/Gui/MyViewer.cpp	0.00% <0.00%> (ø)
examples/CurveEditor/PointComponent.cpp	0.00% <0.00%> (ø)
... and 16 more

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[dlyr]

superseed by #967