[Constraint.Projective] Make LinearVelocityProjectiveConstraint work with FreeMotionAL

[bakpaul]

Implement missing methods to work in FreeMotionAnimationLoop. --> simply took what was implemented in FixedProjectiveConstraint.

Also add a new feature to keep the constraint applied after all the key event have passed

[ci-depends-on https://github.com/sofa-framework/Regression/pull/72]

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[bakpaul]

[ci-build][with-all-tests]

[sofabot]

[ci-depends-on] detected during build #8.

To unlock the merge button, you must

• Merge or close https://github.com/sofa-framework/Regression/pull/72 _For this build, Regression/ExternalProjectConfig.cmake.in will be edited by builders with GIT_REPOSITORY https://github.com/sofa-framework/Regression GITTAG 8a0390876782ad6852bae2d42944a54d8cd7acf4