Create a helper function to handle project ID qualification

Problem/Motivation

In Project Browser, project IDs are always fully qualified Composer-style -- i.e., SOURCE_ID/LOCAL_ID. There are a bunch of places in the code where we're hard-coding that knowledge. It would be better if we could do it in a central spot.

Proposed resolution

Create a public static helper function in Normalizer that can take either a string or an array. If given a string, it explodes it into the two parts. If given in array, it joins them.