Don't pull in the entire Rx.js library

[jbgarr]

As discussed in this issue it seems that for the System.js version of clarity-seed, the entire Rx.js library is being pulled in. This creates 343 requests related to the Rx.js library each time the seed project is fired up or reloaded. That makes for a pretty painful development experience.

I've suggested a fix in the mentioned issue to help reduce the number of requests so that only the parts of the RX.js library used by the Clarity components are pulled in (by creating a rxjs-operators.ts file). It's also the suggested method laid out by the Angular team.