- input parser recognizes "sqrt()", which is also used in the output

- input parser recognizes "sqrt()", which is also used in the output
- divide(a,b,q) only modifies q if the division succeeds; also, divide(a,b,a)
  works now
- fixed small bug in dummy index renaming which could cause it to not
  recognize renamable indices in some cases
- power::degree() and power::ldegree() throw an exception when encountering
  a non-integer exponent