Refactor Affine3d -> Isometry3d (Melodic)

[henningkayser]

This PR changes all references to the in melodic obsolete type Eigen::Affine3d to Eigen::Isometry3d.
(required for the melodic-devel branch of moveit_grasps)

[mlautman]

My only concern is that this may be being used by someone outside of the MoveIt! community. Perhaps leave the old headers and point them to the isometry versions? Even better would be to use the same fancy templating that gets used in the Eigen project... but that may be too much to ask

[henningkayser]

I think Affine3d shouldn't be used anymore since it's just the wrong type in the robotics context.
What do you think of making the functions deprecated and moving the implementation to the header?

[henningkayser]

@mlautman I added the changes described above. Affine3d is still supported but now deprecated using the C++14 specifiers.