Wallet LMDB backend (#1151)

* Migrate main node store to LMDB

In preparation to using LMDB as a wallet database, migrate the
node db. There's no point in having 2 key-value stores.
In addition LMDB provides a few advantages as a node db, namely a
much faster build (compared to RocksDb), lesser dependencies and
transactions.

* Migrated p2p store to lmdb, stuff compiles

* More fixes, chain tests starting to pass

* Fixed txhashset rollback messing with block save and general batch delimitation. Chain tests passing.

* rustfmt

* LMDB max map size of 10MB isn't really workable. Half TB seems reasonable.

* Fix wallet tests

* Rather crucial commit was missing

* rustfmt

* Fixing new merged tests following lmdb changes

* rustfmt

* * Make txhashset validation read-only on fast sync to avoid having
a really long open transaction.
* Fix deadlock in new block processing, batch should always be
created within a txhashset lock (when they interact).

* Comment about batch and txhashset interlacing

* Fix store tests to use batch

* Externalize wallet config and seed

* Converted direct read access to file outputs map to an iterator

* Cleaned up and simplified wallet Backend trait:

* No more direct mutable access to internal structures (HashMap)
* Batch interface for all writes
* Remove unneeded read wrapper (read_wallet)

* rustfmt

* First (incomplete) pass at wallet LMDB backend

* Progressing on lmdb backent iml

* Added batch impl for LMDB wallet backend. Pretty much done with it, but not sure how to deal with commit (owned).

* rustfmt

* Wrapping LMDB batch around a refcell to work around borrow rules

* Compilation up to grin chain

api/src/handlers.rs

@@ -496,21 +496,6 @@ impl Handler for ChainValidationHandler {
 	}
 }
 
-/// Temporary - fix header by height index.
-/// POST /v1/chain/height-index
-pub struct HeaderByHeightHandler {
-	pub chain: Weak<chain::Chain>,
-}
-
-impl Handler for HeaderByHeightHandler {
-	fn handle(&self, _req: &mut Request) -> IronResult<Response> {
-		match w(&self.chain).rebuild_header_by_height() {
-			Ok(_) => Ok(Response::with((status::Ok, ""))),
-			Err(_) => Ok(Response::with((status::InternalServerError, ""))),
-		}
-	}
-}
-
 /// Chain compaction handler. Trigger a compaction of the chain state to regain
 /// storage space.
 /// GET /v1/chain/compact
@@ -733,9 +718,6 @@ pub fn start_rest_apis<T>(
 			let chain_compact_handler = ChainCompactHandler {
 				chain: chain.clone(),
 			};
-			let header_height_handler = HeaderByHeightHandler {
-				chain: chain.clone(),
-			};
 			let chain_validation_handler = ChainValidationHandler {
 				chain: chain.clone(),
 			};
@@ -795,7 +777,6 @@ pub fn start_rest_apis<T>(
 				chain_compact: get "/chain/compact" => chain_compact_handler,
 				chain_validate: get "/chain/validate" => chain_validation_handler,
 				chain_outputs: get "/chain/outputs/*" => output_handler,
-				header_height: post "/chain/height-index" => header_height_handler,
 				status: get "/status" => status_handler,
 				txhashset_roots: get "/txhashset/*" => txhashset_handler,
 				pool_info: get "/pool" => pool_info_handler,