2
Revert c3908a2..ccda8c5

This rolls back to commit c3908a2164fcb80f0496c80fd2958c5a3bde88d6.
support for polynomial expansion

expand (Power (Plus [a,b]) 5) returns
((10*a^(2)*b^(3))+(10*a^(3)*b^(2))+(5*a*b^(4))+(5*a^(4)*b)+a^(5)+b^(5)),
 as it should