Introduce kotlin and reimplement RN-timers idling resource

[d4vidi]

Description:

1. Introduce Kotlin into detox core (lib)
2. Reimplement the ReactNativeTimersIdlingResource in Kotlin, TDD.

[d4vidi]

NOTE still need to check the effect kotiln would have on a potential detox .aar.
NOTE 2 still need to verify versioning collision and the minimal kotlin version.
In any case, I think we should publish this under a new major (or at least a minor)

[d4vidi]

Follow-up on the notes:

Seems there are plenty of Kotlin based .aar/.jar's out there. I've taken a deep look into some and it seems that while the delivered bytecode expects the presence of Kotlin elements (e.g. functions return kotlin.String), kotlin core is never bundled in. Rather, the hosting app should introduce Kotlin stdlib in its deps and - as long as the version is new enough (tested 1.1.0 in our case), it should all play nice together eventually.

As for versioning -- I worked out detox to default to 1.3.0 but to also expect the version to be defined by the hosting app by aligning a global called detoxKotlinVersion to their own kotlin version. We'll add that to the installation instructions and everything should be ok.

[d4vidi]

Next up, we have the CI saying: > Plugin with id 'kotlin-android' not found. @yershalom and I are trying to figure out why gradle doesn't download it automatically.

[d4vidi]

@rotemmiz you oughta change the project's settings to deny merging as long as checks haven't succeeded + view approved...

[yershalom]

@d4vidi Maybe related to this? https://shift.infinite.red/could-not-find-com-tools-build-gradle-2-3-3-8f586ad813ab

[d4vidi]

@yershalom holy c***, giving it a try...

[rotemmiz]

@d4vidi what's the verdict? Were you able to solve it?

[d4vidi]

@rotemmiz ios builds fail in very weird ways. I'm trying to figure where this is coming from, though in essence this PR has nothing to do with iOS at all.

[d4vidi]

@yershalom connectivity issues? -

10:20:52 lerna info Installing external dependencies
... ( >4 minutes)
10:25:01 lerna ERR! execute callback with error
10:25:01 lerna ERR! Error: Command failed: npm install

'only other thing I can think of is changing the ver to 10.0.0, but that shouldn't matter, should it?

[d4vidi]

I know what this is about. I'm taking care of it.

[d4vidi]

Fixes issue #1115