Failing app fixes

[jsl12]

• Respecting the disable key in app configurations when
  • processing module import order
  • processing app start order
• Fixed a bug where a failed app could get re-introduced to the start order only to fail again
• Fixed a bug where changing files at exactly right time would throw an error
• Files with syntax errors get added to bad_files list, even if they aren't used for apps
• Improved error text for ImportErrors and SyntaxErrors in user apps