Checklist

• Appropriate branch selected => Updating the mtc-deploy branch at this time
• [na] Any modified or new methods or classes have helpful JSDoc and code is thoroughly commented
• [na] The description lists all applicable issues this PR seeks to resolve
• [na] The description lists any configuration setting(s) that differ from the default settings
• All tests and CI builds passing

Description

This PR brings changes from the dev branch to the mtc-deploy branch and resolves conflicts between the two branches.

Many of the changes are just i18n, improved Flow types, or Bootstrap syntax updates, so when you see them you can just skim them. Weird indents are sometimes brought in from the dev branch, I have not really attempted to fix them.

A few things that needed to be fixed in this PR for the MTC UI to work:

• Alerts Viewer UI was updated to newest bootstrap syntax (so that the collapsible panes for each alert keep working)
• The AppInfoRetriever component is modified to wrap the app contents, so that nothing is rendered until the app info JSON is downloaded and customizations can be applied (e.g. title, logo, link to alerts module).
• When creating a new route in the GTFS editor, the following defaults are maintained: route status = "in progress", route approval state = "not approved".