I still do not really understand it, but I believe it is
correct nevertheless.

[[Imported from SVN: r9282]]

[[Imported from SVN: r8627]]

There were two issues fixed by this patch:

a) The bending energy only involves the third director.
   One must look at it as a function in S^2, not as
   a subset of coefficients of a function to SO(3).
   This means that we have to use a different projection
   in one place.
b) A certain subset of the coefficients (see the code)
   must always be zero, because they are parts of
   3-vectors which are known to be perpendicular to (0,0,1).
   For some strange reason they aren't.  I now hardwire
   them to be 0 anyway.  This makes my test pass.
   Maybe one day I'll find the true reason :-)

[[Imported from SVN: r8626]]

of Neumann boundary forces.  But I am not sure and I want to
postpone the issue.  Therefore this patch adds a cpp warning.

[[Imported from SVN: r8625]]

Don't use a loop with 4 iteration to clear an array,
if the array has only length 3.

Boy, this did take a while to find...

[[Imported from SVN: r8593]]

[[Imported from SVN: r8572]]

[[Imported from SVN: r8571]]

[[Imported from SVN: r8570]]

[[Imported from SVN: r8569]]

Because trace(sym(A)) == trace(A)

[[Imported from SVN: r8568]]

[[Imported from SVN: r8567]]

[[Imported from SVN: r8566]]

[[Imported from SVN: r8565]]

[[Imported from SVN: r8409]]

implement the remaining curvature and bending terms for the energy gradient.  These are not working yet, though.

[[Imported from SVN: r8408]]

So far, the long form of the quadratic bending energy has been
implemented and tested, and it appears to do the right thing.

This is a snapshot commit.  The code remains out-commented until
it is finished.

[[Imported from SVN: r8403]]

[[Imported from SVN: r8364]]

we know the function value when calling evaluateDerivative.  So let's give that value to the method, to prevent it from recomputing it

[[Imported from SVN: r8363]]

Use the long form for the quadratic energy stiffness.  I tested it: when kappa=1 is does the same as the short form

[[Imported from SVN: r8308]]

[[Imported from SVN: r8307]]

to set the shear correction factor.

[[Imported from SVN: r8290]]

[[Imported from SVN: r8182]]

target space classes.  In particular, the coordinate type
now has to be given explicitly.

[[Imported from SVN: r8149]]

[[Imported from SVN: r8024]]

[[Imported from SVN: r8023]]

[[Imported from SVN: r7923]]

[[Imported from SVN: r7888]]

[[Imported from SVN: r7887]]

[[Imported from SVN: r7868]]

[[Imported from SVN: r7867]]

[[Imported from SVN: r7842]]

[[Imported from SVN: r7611]]

[[Imported from SVN: r7567]]

[[Imported from SVN: r7566]]

coordinates into a separate method, and fix an index bug on the way.
Now this derivative passes an fd check.

[[Imported from SVN: r7565]]

[[Imported from SVN: r7564]]

[[Imported from SVN: r7560]]

[[Imported from SVN: r7559]]

[[Imported from SVN: r7558]]

[[Imported from SVN: r7557]]