Take the 'Sum' out of 'Sumtree' (#702)

* beginning to remove sum

* continuing to remove sumtree sums

* finished removing sums from pmmr core

* renamed sumtree files, and completed changes+test updates in core and store

* updating grin/chain to include removelogs

* integration of flatfile structure, changes to chain/sumtree to start using them

* tests on chain, core and store passing

* cleaning up api and tests

* formatting

* flatfiles stored as part of PMMR backend instead

* all compiling and tests running

* documentation

* added remove + pruning to flatfiles

* remove unneeded enum

* adding sumtree root struct

keychain/src/keychain.rs

@@ -29,9 +29,9 @@ use blind::{BlindSum, BlindingFactor};
 use extkey::{self, Identifier};
 
 #[cfg(feature = "use-bullet-proofs")]
-const USE_BULLET_PROOFS:bool = true;
+pub const USE_BULLET_PROOFS:bool = true;
 #[cfg(not(feature = "use-bullet-proofs"))]
-const USE_BULLET_PROOFS:bool = false;
+pub const USE_BULLET_PROOFS:bool = false;
 
 #[derive(PartialEq, Eq, Clone, Debug)]
 pub enum Error {