Fix broken iOS app build by downgrading Firebase iOS dependencies

Fixes

1. iOS: Downgrading the Firebase iOS dependency to 5.x to make the iOS app build fixed.
2. Common: Removed deprecated getInstanceId method. Use getToken instead.

Code diff: v5.0.0...v5.1.0

Major Change: Using CocoaPods to install Firebase iOS dependencies which requires minimum cordova-lib/cordova-cli v9

Major Change

1. iOS: Using CocoaPods to manage Firebase dependencies hence requires cordova-cli to be minimum v9.0.0.
2. Docs: Detailed instructions to get the Cordova environment versions and different major releases to be used.

Code diff: v4.1.0...v5.0.0

Merged two method to log errors, edge case scenario handling

Changes

1. Breaking change: Removed method logJSError (introduced in v3.2.0) and merged that into logError message.
2. Android: Handling a few edge cases for logError method.
3. Docs: Adding more docs in README.md
4. Docs: Sorting & improving API docs
5. Docs: Generating "Table of Contents" for README & API docs.

Code diff: v4.0.1...v4.1.0

Fixed a typo in firebase-browser.js

Code diff: v4.0.0...v4.0.1

Breaking Change - Minimum cordova-android 8.0.0 required

Changes

1. Fix app build due to breaking changes released by Google Firebase on Jun 17, 2019. #13

Code diff: v3.3.0...v4.0.0

Last version supporting cordova-android 7.x.x

Changes

1. Fix app build due to breaking changes released by Google Firebase on Jun 17, 2019.

Code diff: v3.2.0...v3.3.0

Ability to log JS stracktrace

New Features

1. Added ability to log JavaScript stacktrace with a new method logJSError. Thanks to distinctdan for
   PR#8.

Code diff: v3.1.0...v3.2.0

Support for creating "Notification Channels" on Android O

New Features

1. Added support for creating Notification Channels on Android O. Thanks to Maximilian Loy for the contribution
2. Formatting codebase to use 4 spaces

Code diff: v3.0.0...v3.1.0

Maintained by Wiz Panda

Changes/differences from the original repository

1. Cordova@9 support
2. Fixes issues caused by Firebase SDK updates on 5 April 2019.
   Thanks to Dave Alden for commit
3. Remove obsolete entry for FirebasePluginInstanceIDService. Thanks to Dave Alden for commit
4. Remove unnecessary extra block which can lead to race condition. Thanks to Dave Alden for commit
5. Remove redundant build-extras.gradle. Thanks to Dave Alden for commit