Translations:FEM ConstraintDisplacement/8/en

For the solver CalculiX:
 * The constraint uses the *BOUNDARY card.
 * Fixing a degree of freedom is explained at http://web.mit.edu/calculix_v2.7/CalculiX/ccx_2.7/doc/ccx/node164.html
 * Prescribing a displacement for a degree of freedom is explained at http://web.mit.edu/calculix_v2.7/CalculiX/ccx_2.7/doc/ccx/node165.html