Previously, this test used a situation with geodesic interpolation
between two points on the sphere that are almost antipodal.
This made the TargetSpaceRiemannianTRSolver crash, because the
weighted sum of squared distances can have indefinite second
derivatives in such a situation.  In principle, the
TargetSpaceRiemannianTRSolver should handle this, but nowadays
it is not actually a TR solver anymore, but a plain local
Newton method.  Maybe I should revert back to trust-region.

I added a comment to targetspacetrsolver.cc that explains the
situation a little.

This resolves a name ambiguity.

This makes the test build again.

It also removes the FD test for the gradient of the harmonic energy.
Since the HarmonicEnergyStiffness class does not implement the
gradient anymore, there is nothing to test here.

[[Imported from SVN: r8352]]

[[Imported from SVN: r8054]]

[[Imported from SVN: r8053]]

This is needed to test quad elements and higher-order gfe.

[[Imported from SVN: r8047]]

[[Imported from SVN: r7132]]

[[Imported from SVN: r7124]]

[[Imported from SVN: r7123]]

[[Imported from SVN: r7122]]

[[Imported from SVN: r7121]]

[[Imported from SVN: r7040]]

[[Imported from SVN: r5940]]

[[Imported from SVN: r5928]]

[[Imported from SVN: r5665]]