Fixed another bug "install" => "build".
Specify minimum version.
Remove environment from per-package configuration.
Improve code documentation.
Enable Package to be used in a set/hash key.
Make options read/write.
Add a method to compute unresolved packages.
Improve the materialization code to deal with imported imports and configuration options correctly.
Ensure that all package configurations contain a link to their own targets/generators.
Improve support for listing imports and fetch now works as packages become available/materialized.
Print elapsed time to stderr so it doesn't interfer with stdout.
Add a environment command, mostly for debugging.
Tidy up init project generation code.
Defer more logic to the Loader, and add support for Configuration visibility.
Added experimental merge support to generators.
Application directory "apps" => "Applications"
Minor updates to README.