Use newly added Path.package to get package directory
Add specific crawlers for different cases
move data structures to Utils/ and add Build.initEnv
Switch to Module.Interface from the compiler
Stop testing Build.Display in Main
begin to bridge gap between Crawl and Build

- Begin writing Prep module to load interfaces and generally prep for
building
- Move all crawl code to Crawl.DepthFirstSearch
- Move graph reversal and cycle checks to Prep