Bulletproofs+ (#70)

* Initial stab at Bulletproofs+

Does move around the existing Bulletproofs code, does still work as 
expected.

* Make the Clsag RCTPrunable type work with BP and BP+

* Initial set of BP+ bug fixes

* Further bug fixes

* Remove RING_LEN as a constant

* Monero v16 TX support

Doesn't implement view tags, nor going back to v14, nor the updated BP 
clawback logic.

* Support v14 and v16 at the same time

coins/monero/src/ringct/clsag/mod.rs

@@ -12,8 +12,8 @@ use curve25519_dalek::{
 };
 
 use crate::{
-  Commitment, random_scalar, hash_to_scalar, transaction::RING_LEN, wallet::decoys::Decoys,
-  ringct::hash_to_point, serialize::*,
+  Commitment, random_scalar, hash_to_scalar, wallet::decoys::Decoys, ringct::hash_to_point,
+  serialize::*,
 };
 
 #[cfg(feature = "multisig")]
@@ -292,8 +292,8 @@ impl Clsag {
     Ok(())
   }
 
-  pub(crate) fn fee_weight() -> usize {
-    (RING_LEN * 32) + 32 + 32
+  pub(crate) fn fee_weight(ring_len: usize) -> usize {
+    (ring_len * 32) + 32 + 32
   }
 
   pub fn serialize<W: std::io::Write>(&self, w: &mut W) -> std::io::Result<()> {