[[Imported from SVN: r1554]]

[[Imported from SVN: r1553]]

[[Imported from SVN: r1552]]

add verification code to check whether the output pressure field really has the wanted total force and torque

[[Imported from SVN: r1544]]

[[Imported from SVN: r1535]]

[[Imported from SVN: r1534]]

[[Imported from SVN: r1529]]

[[Imported from SVN: r1528]]

[[Imported from SVN: r1525]]

[[Imported from SVN: r1524]]

[[Imported from SVN: r1510]]

[[Imported from SVN: r1506]]

[[Imported from SVN: r1505]]

Add a method to assemble the Hessian matrix by a finite difference
approximation.

[[Imported from SVN: r1504]]

[[Imported from SVN: r1503]]

[[Imported from SVN: r1502]]

fixed one indexing bug in the hessian computation; added various helper methods for the derivatives of the strains and fd approximations for them

[[Imported from SVN: r1501]]

[[Imported from SVN: r1495]]

[[Imported from SVN: r1494]]

[[Imported from SVN: r1473]]

[[Imported from SVN: r1472]]

[[Imported from SVN: r1471]]

[[Imported from SVN: r1470]]

[[Imported from SVN: r1469]]

[[Imported from SVN: r1468]]

[[Imported from SVN: r1220]]

[[Imported from SVN: r1206]]

[[Imported from SVN: r1124]]

[[Imported from SVN: r1123]]

[[Imported from SVN: r1118]]

[[Imported from SVN: r1117]]

[[Imported from SVN: r1116]]

[[Imported from SVN: r1115]]

[[Imported from SVN: r1109]]

bugfix: the explicit expression for the Darboux vector given by Dichmann is already in local coordinates

[[Imported from SVN: r1105]]

[[Imported from SVN: r1104]]

[[Imported from SVN: r1103]]

[[Imported from SVN: r1093]]

[[Imported from SVN: r1092]]

[[Imported from SVN: r1091]]