Add support for tvOS

[shvul]

PROBLEM

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Add support for tvOS #640

SOLUTION

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• updated XCTest headers
• update dependencies
• added new endpoints (for remote control, elements focusing)
• added new targets for tvOS
• implemented new integration app for tvOS
• implemented separate uittests suite for atv
• adopted iOS unit tests to tvOS specific and created new ones
• fixed hit test issues (major logic is taken from Appium)
• update inspector
• updated build script and travis configuration

NOTES

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As I already mention, I added functionality to perform element explicit focusing. You requested this feature at #195
Tests suite is green

[mykola-mokhnach]

I would say it makes sense to split the PR into multiple smaller chunks. It is impossible to review such a big amount of source code.

[shvul]

@mykola-mokhnach I divided tvOS related logic in smaller chunks. Here is the first one: #1032

[mykola-mokhnach]

Thanks @shvul
I think there was already a similar PR, but the owner did not have time to split it. Also, be ready to wait for a while until you get a reply from the repo owner(s)

[g-tiwari]

Do we have any update on this integration ?
@shvul I would love to help if anything is needed.