Hotfix: Apostrophe 3.0.1 fixes issues with multiple ui/src/index.js files

[boutell]

We've just corrected a bug in Apostrophe 3.0.0 that impacts developers taking advantage of our new ui/src feature. Here are the changes:

• Fixed an error observed in the browser console when using more than one ui/src/index.js file in the same project. Using more than one is a good practice as it allows you to group frontend code with an appropriate module, or ship frontend code in an npm module that extends Apostrophe.
• Migrated all of our own frontend players and utilities from ui/public to ui/src.
• Executed ui/src imports without waiting for next tick, which is appropriate as we see it as an alternative to ui/public, which has always been run without delay.