Make Nova's ecc gadgets read curve parameters from the group trait (#115)

* make ecc gadgets defined over Group rather than PrimeField

* use curve parameters from Group trait

src/traits/mod.rs

@@ -12,6 +12,7 @@ use merlin::Transcript;
 use num_bigint::BigInt;
 
 /// Represents an element of a group
+/// This is currently tailored for an elliptic curve group
 pub trait Group:
   Clone
   + Copy
@@ -62,14 +63,14 @@ pub trait Group:
   /// Returns the affine coordinates (x, y, infinty) for the point
   fn to_coordinates(&self) -> (Self::Base, Self::Base, bool);
 
-  /// Returns the order of the group as a big integer
-  fn get_order() -> BigInt;
-
   /// Returns an element that is the additive identity of the group
   fn zero() -> Self;
 
   /// Returns the generator of the group
   fn get_generator() -> Self;
+
+  /// Returns A, B, and the order of the group as a big integer
+  fn get_curve_params() -> (Self::Base, Self::Base, BigInt);
 }
 
 /// Represents a compressed version of a group element