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/json_tests/state.rs

@@ -62,7 +62,8 @@ pub fn json_chain_test(json_data: &[u8], era: ChainEra) -> Vec<String> {
 				let mut state_result = get_temp_state();
 				let mut state = state_result.reference_mut();
 				state.populate_from(pre);
-				state.commit();
+				state.commit()
+					.expect(&format!("State test {} failed due to internal error.", name));
 				let vm_factory = Default::default();
 				let res = state.apply(&env, engine.deref(), &vm_factory, &transaction, false);