v5.5.4 react-native-firebase, new SDK Pods+Android, RN0.59.9

[mikehardy]

I updated the react-native-firebase-starter to

• react-native 0.59.9
• react-native-firebase v5.5.4 (including breaking changes migrations)
• most recent non-AndroidX android libraries
• most recent iOS libraries
• most recent knowledge about bundling in android dev (from react-native PR I had merged then had to revert! ouch)
• most recent dependency resolution stuff

When I made these changes, did a rename, then plopped my tester .json/plist files into place it seemed to run fine on android and ios

This is the front door for the project so I think I got things right, but you'd probably want to reproduce it?

Fixes #104