test/transformation: Switch to smart pointers

Use smart pointers for construction tests instead
of using `new` directly inside the Boost test
macros.
transformation/orthogonal: Rename parameter

Rename parameter for consistency between
OrthogonalDepthProjection and
OrthogonalProjection. 'direction' even doesn't
make much sense (you don't know if you mean the
spanning directions or the normal/lookat
direction). So now call it 'lookat'.
orthogonal_depth_projection: Change constructor

Construct from `const` reference, not from copy!
orthogonal_depth_projection: Add new constructor

Add constructor that is also supported in base
class. This includes tests for the new
constructor.
transformation: Documentation update

Update documentation comments for
OrthogonalProjection and
OrthogonalDepthProjection.