Core tracedb functionality. (#996)

* fixed encoding 0u8

* simplified if else stmt

* tracedb core

* more comprehensive tracedb tests

* fixed minor review issues

* addresses filter

* fixed typos

* replace malformed with corrupted

* trace switch

* db key is generic and can be made smaller

* smaller tracedb keys

* tracedb version

* fixed ignored tests

* rename Tracedb -> TraceDB

* fixed typos

* proves

* trace only top level calls to builtins to avoid DDoS attacks

* fixed tracedb config switches

* fix comments fat replaced with trace

* vector-addressing scheme for localized traces

* removed comments

* removed first, redundant 0 from trace address

* updated db.trace method

* additional tests for tracedb.trace()

ethcore/src/client/config.rs

@@ -16,6 +16,7 @@
 
 pub use block_queue::BlockQueueConfig;
 pub use blockchain::BlockChainConfig;
+pub use trace::{Config as TraceConfig, Switch};
 use util::journaldb;
 
 /// Client configuration. Includes configs for all sub-systems.
@@ -25,6 +26,8 @@ pub struct ClientConfig {
 	pub queue: BlockQueueConfig,
 	/// Blockchain configuration.
 	pub blockchain: BlockChainConfig,
+	/// Trace configuration.
+	pub tracing: TraceConfig,
 	/// The JournalDB ("pruning") algorithm to use.
 	pub pruning: journaldb::Algorithm,
 	/// The name of the client instance.