Include default values in storage metadata (#1264)

* Add a 'default' field to metadata. It contains code to generate the
default value.

* wasm update

* Make 'default' field an `Option`

* Boxed fn is not static, that won't be fine

* static fn won't do it to as it cannot get T param, will try fat trait

* Fat pointer over phantom data compatible with static instantiation

* DecodeDifferent is cool, using it for decoding.

* using once cell to do what would require copying lazy_static internals.

* Remove cache when no_std (non compatible deps)

* wasm bins update

* Fuse tooling struct and enum derive.

substrate/node/runtime/wasm/Cargo.lock

@@ -564,6 +564,11 @@ dependencies = [
  "libc 0.2.44 (registry+https://github.com/rust-lang/crates.io-index)",
 ]
 
+[[package]]
+name = "once_cell"
+version = "0.1.6"
+source = "registry+https://github.com/rust-lang/crates.io-index"
+
 [[package]]
 name = "openssl"
 version = "0.10.15"
@@ -1283,6 +1288,7 @@ version = "0.1.0"
 dependencies = [
  "hex-literal 0.1.1 (registry+https://github.com/rust-lang/crates.io-index)",
  "mashup 0.1.9 (registry+https://github.com/rust-lang/crates.io-index)",
+ "once_cell 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)",
  "parity-codec 2.1.5 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde 1.0.81 (registry+https://github.com/rust-lang/crates.io-index)",
  "serde_derive 1.0.81 (registry+https://github.com/rust-lang/crates.io-index)",
@@ -1991,6 +1997,7 @@ dependencies = [
 "checksum num-integer 0.1.39 (registry+https://github.com/rust-lang/crates.io-index)" = "e83d528d2677f0518c570baf2b7abdcf0cd2d248860b68507bdcb3e91d4c0cea"
 "checksum num-traits 0.2.6 (registry+https://github.com/rust-lang/crates.io-index)" = "0b3a5d7cc97d6d30d8b9bc8fa19bf45349ffe46241e8816f50f62f6d6aaabee1"
 "checksum num_cpus 1.8.0 (registry+https://github.com/rust-lang/crates.io-index)" = "c51a3322e4bca9d212ad9a158a02abc6934d005490c054a2778df73a70aa0a30"
+"checksum once_cell 0.1.6 (registry+https://github.com/rust-lang/crates.io-index)" = "d7ce3535d54560c937c1652ba4a0da66bfc63e0f8e07bed127483afb6e5ee925"
 "checksum openssl 0.10.15 (registry+https://github.com/rust-lang/crates.io-index)" = "5e1309181cdcbdb51bc3b6bedb33dfac2a83b3d585033d3f6d9e22e8c1928613"
 "checksum openssl-sys 0.9.39 (registry+https://github.com/rust-lang/crates.io-index)" = "278c1ad40a89aa1e741a1eed089a2f60b18fab8089c3139b542140fc7d674106"
 "checksum owning_ref 0.3.3 (registry+https://github.com/rust-lang/crates.io-index)" = "cdf84f41639e037b484f93433aa3897863b561ed65c6e59c7073d7c561710f37"