Merge tests for rotations and quaternions, found failing tests

[SamFlt]

• Verify that operator= of vpQuaternionVector works as intended
• Merge testQuaternion.cpp and testQuaternion2.cpp under the catch2 framework
• Merge testRotation.cpp and testRotation2.cpp under the catch2 framework
• Fix failing test. Adding more tests wrt to rotation representations and conversions highlighted an issue in converting from a vpRotationMatrix to a vpRzyxVector (see section "Conversion from and to rzyx vector" of the proposed testRotation.cpp)

This failing test results in :

Initialization vpRzyxVector 
64: 3.141592654
64: 2.094395102
64: 0.7853981634
64: From vpRzyxVector to vpRotationMatrix  
64: 0.5  -0.6123724357  -0.6123724357
64: -6.123233996e-17  -0.7071067812  0.7071067812
64: -0.8660254038  -0.3535533906  -0.3535533906
64: From vpRotationMatrix to vpRzyxVector 
64: rzyx(3,1) = [-1.224646799e-16
64: 1.047197551
64: -2.35619449]
64: Test fails: bad content