message: Quil visitor use theta string rather than trying to cast to double
  This is problematic when there is a U3 gate: it will create a Ry with string param, then revisit.
diff: @@ -146,7 +146,7 @@ public:
  quilStr += "RY("+angleStr+") " + qubit + "\n";
  } else {
  Rx rx1(ry.bits()[0], xacc::constants::pi/2.);
  - Rz rz1(ry.bits()[0], ry.getParameter(0).as<double>());
  + Rz rz1(ry.bits()[0], angleStr);
  Rx rx2(ry.bits()[0], -xacc::constants::pi/2.);
  visit(rx1);
  