eina_quaternion: add forgotten implementation of converting eina_matrix3 to eina_quat...

eina_quaternion: add forgotten implementation of converting eina_matrix3 to eina_quaternion

Summary:
Implemenation of eina_matrix3_quaternion_get function

Signed-off-by: Vivek Ellur <vivek.ellur@samsung.com>
Reviewers: cedric

Subscribers: cedric

Differential Revision: https://phab.enlightenment.org/D2786

This was a function I forgot to finish implement. Thanks Vivek to take care of it.
As it comes with a test case, is self contained and fix a missing bit of code I will
push it at this point in time of our release process. Sorry everyone for that late push.

Signed-off-by: Cedric BAIL <cedric@osg.samsung.com>