added resort_particle at beginning of integration, misc fixes to bending force scheme, removed redundant code in ibm_coupling
doxygen comments for bending_ibm
changed ifdef in integrate_vv, added bending force test in testsuite
added another test case for bending_force_ibm
ifedfs for tcl callback functions of ibm and renamed stretching law callback in the header file
returned ibm methods to lb file, ifdef for lb force calculation in force_calc to work with ibm, commented wrong vecsub line in stretching_force_calc, renamed method to get_interpolated velocity for virtual sitesibm