update docstrings of multilinear terms, see #773
update docstrings of multilinear terms, see #773

rc/sfepy,rc/sfepy,BubuLK/sfepy,vlukes/sfepy,BubuLK/sfepy,vlukes/sfepy,rc/sfepy,sfepy/sfepy,vlukes/sfepy,sfepy/sfepy,sfepy/sfepy,BubuLK/sfepy