The rotation of oif's was corrected
New force added, called stretchlin, it is almost the same as streching force, however, in stretching force the string defined by this force is nonlinear, with neo-hookean dependence of stiffness constant. Stretchlin is purely linear.
One file fortgotton in previous commit
Merge branch 'espressomd_master' into espresso-object-in-fluid

Conflicts:
	src/Makefile.am
	src/energy.h
	src/forces.h
	src/tcl/interaction_data_tcl.c
Removed remaining fsi files
scripts/object-in-fluid.tcl - Generation of bending forces changed. Now, bending forces are generated only for those edges that have two triangles next to them. This means, that also open objects can be simulated.
Merge Ivan's changes