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/RestQuery.spec.js

@@ -9,11 +9,17 @@ var querystring = require('querystring');
 var request = require('request');
 var rp = require('request-promise');
 
-var config = new Config('test');
-let database = config.database;
+var config;
+let database;
 var nobody = auth.nobody(config);
 
 describe('rest query', () => {
+
+  beforeEach(() => {
+    config = new Config('test');
+    database = config.database;
+  });
+
   it('basic query', (done) => {
     rest.create(config, nobody, 'TestObject', {}).then(() => {
       return rest.find(config, nobody, 'TestObject', {});