Fix sandbox::Memory lifecycle + sandox get memory function for no_std env (#845)

* Fix `sandbox::Memory` lifecycle for no_std env

* Retain memories in env_def builder and instance

* Add scoped memory creation to test RC semantics

* Add deploying_wasm_contract_should_work test.

* Fix sandboxed memory set function.

substrate/Cargo.lock

@@ -1611,6 +1611,7 @@ dependencies = [
  "sr-primitives 0.1.0",
  "srml-balances 0.1.0",
  "srml-consensus 0.1.0",
+ "srml-contract 0.1.0",
  "srml-session 0.1.0",
  "srml-staking 0.1.0",
  "srml-support 0.1.0",
@@ -1623,6 +1624,7 @@ dependencies = [
  "substrate-state-machine 0.1.0",
  "substrate-trie 0.4.0",
  "trie-root 0.9.0 (git+https://github.com/paritytech/trie)",
+ "wabt 0.4.0 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
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