make block queue into a more generic verification queue and fix block heap size calculation (#2095)

* move block queue to own module, a couple readability changes

* make block queue generic over verifiable data

also fixes heap size calculation

* make block queue into a more generic verification queue

* some module reoganization

* implement header queue

* clean up verification error messages

ethcore/src/client/config.rs

@@ -16,11 +16,11 @@
 
 use std::str::FromStr;
 pub use std::time::Duration;
-pub use block_queue::BlockQueueConfig;
 pub use blockchain::Config as BlockChainConfig;
 pub use trace::Config as TraceConfig;
 pub use evm::VMType;
-pub use verification::VerifierType;
+
+use verification::{VerifierType, QueueConfig};
 use util::{journaldb, CompactionProfile};
 use util::trie::TrieSpec;
 
@@ -84,7 +84,7 @@ impl Default for Mode {
 #[derive(Debug, PartialEq, Default)]
 pub struct ClientConfig {
 	/// Block queue configuration.
-	pub queue: BlockQueueConfig,
+	pub queue: QueueConfig,
 	/// Blockchain configuration.
 	pub blockchain: BlockChainConfig,
 	/// Trace configuration.