function osl_relation_poly_sread() added
fixed the reading of unions in osl_relation_poly_psread() function
replaced tab characters by spaces
renamed functions osl_osl_relation_poly_sread() and osl_osl_relation_poly_psread() to osl_relation_sread_polylib() and osl_relation_psread_polylib() respectively
fixed tabulation issues
Merge pull request #22 from cesarsabater/master

Added reading function for reading strings in Extended Polylib textual format and fixed sread for unions of relations