Remove (almost all) panickers from trie module (#1776)

* memorydb ub patch and other cleanup

* fix denote invocations

* move trie traits into trie module

* replace "denote" with shim

* triedb returns results and no longer panics

* fix warnings

* get ethcore compiling

* warn on trie errors in ethcore

* remove unsafety from node decoder

* restore broken denote behavior for this branch

* fix overlayrecent fallout

* fix triedb tests

* remove unwrap in state

* alter Trie::get to return Result<Option<_>>

* fix refcell error in require

* fix test warnings

* fix json tests

* whitespace

[ci:skip]

* Avoid unneeded match/indentation

* whitespace

* prettify map_or_else

* remove test warning

ethcore/src/error.rs

@@ -258,7 +258,10 @@ pub type ImportResult = Result<H256, Error>;
 
 impl From<ClientError> for Error {
 	fn from(err: ClientError) -> Error {
-		Error::Client(err)
+		match err {
+			ClientError::Trie(err) => Error::Trie(err),
+			_ => Error::Client(err)
+		}
 	}
 }
 
@@ -338,6 +341,12 @@ impl From<BlockImportError> for Error {
 	}
 }
 
+impl<E> From<Box<E>> for Error where Error: From<E> {
+	fn from(err: Box<E>) -> Error {
+		Error::from(*err)
+	}
+}
+
 binary_fixed_size!(BlockError);
 binary_fixed_size!(ImportError);
 binary_fixed_size!(TransactionError);