Added also the possibility to use conf.useplot to all functions
Cleaned up the varargout code for wave_field_mono_nfchoa_25d
Added varargout and optinal plotting for nargout==0 to imp functions
Removed unneeded conf.useplot entries from README
Added a working 3D green's function for imp
Add working wave_field_imp function, analogue to wave_field_mono
Added imp functions for simple source models
Implemented missing Green's function for imp and fixed a bug in wave_field_imp_plane_wave
Merge branch 'threed' of github.com:sfstoolbox/sfs into threed

* 'threed' of github.com:sfstoolbox/sfs:
  Added paper to README
  Add 3D syntax to README

Conflicts:
	README.md