Running leo develop with no schema

[ChristopherBiscardi]

Currently, When you run leo develop (often npm start in the starters), you get an error if you haven't updated the schema for the first time.

Option 1: Automatically run "update schema" every time, no matter what.

Option 2: Warn if there is no schema.json file

[ChristopherBiscardi]

webpack's errors for these kinds of issues suck pretty bad from a user perspective. Let's also try to head them off before they hit webpack and provide cleaner messages with more accurate "you should do this next" content.