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, and fixes a few other results for old Firefox versions.

Sorry that the diff looks terrible, but if you run `git diff --minimal`, it more accurately reflects the changes.