[SERVICE-875] Include FDC3 types in @types/openfin

[bryangaleopenfin]

This is a dry-run inclusion of FDC3 types in @types/openfin. This adds FDC3 to index.d.ts and openfin-tests.ts, and follows the preliminary instructions in https://github.com/openfin/Internal-Wiki/wiki/How-to-Update-DefinitelyTyped to add the FDC3 types.

Caveats:

• The FDC3 types were generated from an unreleased version of FDC3 modified to make it simpler to generate types. These changes will need to merged into master and released before we can add FDC3 to @types/openfin
• We will then need a runtime version that uses this version of FDC3, and @types/openfin to be updated against this runtime version, so we can then add the FDC3 types to the correct version
• This bumps the required TypeScript version to 3.0. If this is a problem, another option is changing the occurrences of unknown to any

[tomer-openfin]

We should make sure npm test openfin passes, otherwise, it won't pass their CI.
Also, this needs merging with https://github.com/DefinitelyTyped/DefinitelyTyped/ master

I would've also tucked all the files except for index, tests, and configs in a folder to enable easier versioning in the future.

[licui3936]

It looks to me your PR will be merged into this branch https://github.com/openfin/DefinitelyTyped/tree/fdc3. After that, you will create another PR?

[bryangaleopenfin]

My thinking was this PR to get it into the openfin/DefinitelyTyped fork, so we could do internal review. Then a PR from there in the real DefinitelyTyped.

I used the fdc3 branch originally because I wasn't sure if I was treading on any toes when I started working on this repo!