* feat(Android): implement ConnectionService

Adds basic integration with Android's ConnectionService by implementing
the outgoing call scenario.

* ref(callkit): rename _SET_CALLKIT_SUBSCRIPTIONS

* ref(callkit): move feature to call-integration directory

* feat(ConnectionService): synchronize video state

* ref(AudioMode): use ConnectionService on API >= 26

Not ready yet - few details left mentioned in the FIXMEs

* feat(ConnectionService): add debug logs

Adds logs to trace the calls.

* fix(ConnectionService): leaking ConnectionImpl instances

Turns out there is no callback fired back from the JavaScript side after
the disconnect or abort event is sent from the native. The connection
must be marked as disconnected and removed immediately.

* feat(ConnectionService): handle onCreateOutgoingConnectionFailed

* ref(ConnectionService): merge classes and move to the sdk package

* feat(CallIntegration): show Alert if outgoing call fails

* fix(ConnectionService): alternatively get call UUID from the account

Some Android flavours (or versions ?) do copy over extras to
the onCreateOutgoingConnectionFailed callback. But the call UUID is also
set as the PhoneAccount's label, so eventually it should be available
there.

* ref(ConnectionService): use call UUID as PhoneAccount ID.

The extra is not reliable on some custom Android flavours. It also makes
sense to use unique id for the account instead of the URL given that
it's created on the per call basis.

* fix(ConnectionService): abort the call when hold is requested

Turns out Android P can sometimes request HOLD even though there's no
HOLD capability added to the connection (what!?), so just abort the call
in that case.

* fix(ConnectionService): unregister account on call failure

Unregister the PhoneAccount onCreateOutgoingConnectionFailed. That's
before the ConnectionImpl instance is created which is normally
responsible for doing that.

* fix(AudioModeModule): make package private and run on the audio thread

* address other review comments

This marks our switch to CalVer: http://calver.org/

Major: year
Minor: release number
Patch: build (in case we need to retry)

Load it at build time from a "dropbox.key" file. The file should contain the API
key in a single line.

Used for building and deploying builds to TestFlight and the App Store.

Read it from the GoogleService-Info.plist file and apply it into Info.plist.

No caps are allowed, so this would trigger a rejection when uploading to
TestFlight.

Co-authored-by: DimaG <dgeorgiev06@gmail.com>

This is mostly implemented in the app, with the needed support in the SDK. Since
the app needs to donate intents and deal with creating NSUserActivity objects it
doesn't feel right to do this in a library. Instead, we donate the intents from
the app, but the SDK is ready to extract conference URLs from any intent which
was registered as a conference activity.

This also opens the door for eventually adding Handoff support.

Share the code for extracting the URL for conference from a NSUserActivity.

This is done at the app level, not the SDK.

Currently 2 Firebase services are used:

  - Crashlytics
  - Dynamic Links

They are enabled in tandem, if the appropriate Google services file
(GoogleService-Info.plist on iOS or google-services.json on Android) is found.

Each service needs to be individually enabled in the Firebase console.

Mention the availability of CocoaPods.

Also update the bundle ID since we don't release with that anyway.

Bumping React to 16.6.3 is a requirement for this update.

It doesn't add any value, by default HTTP is not supported unless an exception
is added, plus it doesn't work in browsers at all.

WebRTC no longer actively fixes iOS 9 issues.

Xcode 10 introduced a new build system. Alas, it breaks a number of important
flows, such as creating an archive for the framework (ie SDK) target.

In order to "fix" this, switch back to the former (Xcode 9) build system for the
time being.

The upstream package has been unmaintained for 2 years now, and making the litle
changes needed as React Native needs them is getting old. The actual
funcionality is a couple of one-liners plus tons of boliterplate, which gets
reduced by quite a bit if we just embed it. So here it goes.

When a native iOS module implements `constantsToExport` it must define
`requiresMainQueueSetup`. In this case we don't do any UI stuff so it doesn't
need to be initialized in the main thread.

Make sure both methods offer the same behavior and mark the old one as
deprecated so SDK users get a warning.

This reduces 'xcodebuild' verbosity and fixed problem with exceeding 4MB
of logs size imposed by Travis CI.

It causes false positives when submitting the app to the Store. Use the new
permissions API in react-native-webrtc instead.