Add all alias information to our dependency map, and not just the
aliases that are in use within the application.
Added a new test (currently failing) to show we can display information
for an incomplete alias that is not currently being used, plus added
lots of fail-fast checks to help catch bugs within the code.
Created a SourceModule.assetLocations() method which returns all asset
locations, including transitive dependencies, and switched over to using
that rather than a home baked method, which fixed a bug in the command.
Merge pull request #440 from BladeRunnerJS/dep-insight-improvements

Dep insight improvements