Adds schema caching capabilities (5s by default) (#2286)

* Adds schema caching capabilities (off by default)

* Use InMemoryCacheAdapter

* Uses proper adapter to generate a cache

* Fix bugs when running disabled cache

* nits

* nits

* Use options object instead of boolean

* Imrpove concurrency of loadSchema

* Adds testing with SCHEMA_CACHE_ON

* Use CacheController instead of generator

- Makes caching SchemaCache use a generated prefix
- Makes clearing the SchemaCache clear only the cached schema keys
- Enable cache by default (ttl 5s)

spec/helper.js

@@ -59,7 +59,7 @@ var defaultConfiguration = {
     myoauth: {
       module: path.resolve(__dirname, "myoauth") // relative path as it's run from src
     }
-  },
+  }
 };
 
 let openConnections = {};