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/srml/system/src/lib.rs

@@ -63,7 +63,7 @@ pub fn extrinsics_data_root<H: Hash>(xts: Vec<Vec<u8>>) -> H::Output {
 	H::enumerated_trie_root(&xts)
 }
 
-pub trait Trait: Eq + Clone {
+pub trait Trait: 'static + Eq + Clone {
 	type Origin: Into<Option<RawOrigin<Self::AccountId>>> + From<RawOrigin<Self::AccountId>>;
 	type Index: Parameter + Member + MaybeSerializeDebugButNotDeserialize + Default + MaybeDisplay + SimpleArithmetic + Copy;
 	type BlockNumber: Parameter + Member + MaybeSerializeDebug + MaybeDisplay + SimpleArithmetic + Default + Bounded + Copy + rstd::hash::Hash;