Beam's alpha_i value can also be given as positive value now (internally it needs to be <=0 for incoming beams)

  a result; ideally it should not at all change the internal state;
  definitely it should not store the result.
Comments, layout.

This reverts commit e202d1ef.

Status: FitTest02 fails.

specific implementation RotationZ_3D.
Raw material for all other transforms temporarily moved to
UnusedTransform3D.h.
Status: Core compiles, FunctionalTests not yet.

transform method now in class Transform3D instead of BasicVector3D<>.

'transform' -> 'transformed', no longer in place

Modified API: 'rotate' -> 'rotated', which no longer operates in place.

Doxygen comments.

Formfactors: integrand of imaginary part is real.

Forbid shorthand a*b, request a.dot(b) or dotProduct(a,b).
Remove "virtual" from ~BasicVector3D.
Provide templated implementation for almost all methods,
  resolving issue #237.

Removed duplicate function names (rho, r) from BasicVector3D.