docs: update users guide
docs: update users guide

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