Smash out monero-bulletproofs

Removes usage of dalek-ff-group/multiexp for curve25519-dalek.

Makes compiling in the generators an optional feature.

Adds a structured batch verifier which should be notably more performant.

Documentation and clean up still necessary.

coins/monero/ringct/clsag/Cargo.toml

@@ -52,8 +52,6 @@ std = [
   "zeroize/std",
   "subtle/std",
 
-  "curve25519-dalek/precomputed-tables",
-
   "rand_chacha?/std",
   "transcript?/std",
   "group?/alloc",