add support for custom options questions at app start; refactor index.js

[benjiwheeler]

Resolves

• Resolves https://github.com/LLK/scratchjr/issues/289

Proposed Changes

• add support for custom options questions at app start
• rename AppUsage.js to InitialOptions.js, expand functionality beyond place preference to arbitrary options
• refactor index.js

Testing notes

I tested this in the iOS Simulator and Android Studio Emulator.

I also tested this on an iPad mini running iOS 9.3.5 (which should verify that there is no ES6-specific js)

[chrisgarrity]

The logic to ask the questions looks good, but it looks like it doesn't use the settings each time the app starts. I also have a suggestion for making it localizable even if we don't use localization for the first edition that uses custom options.

[benjiwheeler]

OK, take a look now!

[benjiwheeler]

@chrisgarrity Note that you'll need to change your settings.json file, to replace

            "key": "place",
            "firstTime": true,
            "type": "place"

with

            "key": "place_preference",
            "firstTime": true,
            "type": "place_preference"

[chrisgarrity]

Looks good. I confirmed with both a custom set of user preferences and the old 'place_preference'. Both came through on the analytics.