A few different intertwingled bits.

- Always resolve path to Loc, put it in Loc. We almost always need the full
path, and this simplifies some other use cases.

- Added .codex config file which lives at root of project.

- Added "ignore: prefix, prefix, ..." support in .codex which causes project to
ignore types that match the supplied prefixes when searching, etc. This is
useful for, for example, ignoring java.awt and javax.swing when you're working
on a JavaFX project.