fix an issue where bower_components didn't show up in search

Fixes #2472 - bower_components content not showing up in a search. We no longer consider packages resources to be derived. We now have some utility code to make it easy for builders to ignore packages resource when building however. Essentially, we don't want markers showing up in `packages` or `bower_components`, as this warnings are not something the user can address.

@dinhviethoa