Added tests for each Proxy handler

This adds individual tests for the Proxy `get`, `set`, `has`, `deleteProperty`, `getOwnPropertyDescriptor`, `defineProperty`, `getPrototypeOf`, `setPrototypeOf`, `isExtensible`, `preventExtensions`, `enumerate`, `ownKeys`, `apply` and `construct` handlers. Currently Firefox supports most of them, excepting the prototype handlers and the enumerate handler.

EJS support was inferred from the EJS source.

Also updates the Reflect test to match all the Proxy handlers.