Reorganize app initialization files

[hawkrives]

I'll update all of this later, but this one reorganizes the init stage of the app and the associated folders.

Out and about on my phone at the moment, but I wanted to open this.

There are many more changes here.

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So! This is part of a refurbished, repolished #1537 (the giant reorganization PR). That one tried to do three separate things (move components/ to the top level, reorganize app initialization, and restructure the app views); I've decided to break the changes into smaller chunks for review 😸

This PR is the first of the actual code change PRs; it reorganizes the /source/*.js files that just kinda got stuck in at random times.

• Move the /source/*.js files, except for app and root, into /source/init/
• Rename globals to constants
• Split the navigation imports and navigator creation into two files
• Move trackScreenChanges into a separate file
• Split analytics initialization out of the analytics tracking file
• Centralize IS_PRODUCTION constant into constants.js
• Move things out of /source/init that aren't part of initialization into /source/lib
• Alphabetize the list of Navigation imports

Some of this stuff will move around more in the future, too, but I'm moving them here as well in the interest of smaller PRs.

Timeline

• Move components to source/
• Rename flux/ to redux/
• Reorganize app initialization
• Set up things to we can do import … from '@app/components/colors' instead of import … from '../../../../components/colors'
• Extract reusable views from views/ into modules/
• Automate-ish the loading of views from views/ and deprecate the views.js object