Handle storage with optional modifiers (#717)

* Handle storage with optional modifiers

* Storage docs indicate Option

* Cleanup Option logic

* Convert Optional derive to use Option

* Bump version, update changelog

* Update CHANGELOG description

* Enum.spec.js -> Enum.spec.ts

* Add isEmpty to primitive types

packages/type-storage/package.json

@@ -1,6 +1,6 @@
 {
   "name": "@polkadot/storage",
-  "version": "0.44.1",
+  "version": "0.45.0",
   "description": "Generic wrapper wrapper around state storage",
   "main": "index.js",
   "engines": {
@@ -31,7 +31,7 @@
   "dependencies": {
     "@babel/runtime": "^7.3.1",
     "@polkadot/keyring": "^0.34.20",
-    "@polkadot/types": "^0.44.1",
+    "@polkadot/types": "^0.45.0",
     "@polkadot/util": "^0.34.20",
     "@polkadot/util-crypto": "^0.34.20"
   }

packages/type-storage/src/substrate.ts

@@ -20,7 +20,7 @@ const createRuntimeFunction = (method: string, key: string, { documentation, typ
     new Text(method),
     {
       documentation: new Vector(Text, [documentation]),
-      modifier: new StorageFunctionModifier(0),
+      modifier: new StorageFunctionModifier(1), // default
       type: new StorageFunctionType(type, 0),
       toJSON: (): any =>
         key