Improve exception error when a software is missing
Add a config option for software_gems
Add a config option for local_software_dirs
Use the new configuration options when loading softwares
Refactor the way projects are loaded
Exclude build_version from shasum computation

Some build_version's are based off of a timestamp. Since build_version is used
in the shasumming at the project level (which is then used at the software
level), any project using a timestamp-dependent build_version would not
properly leverage git caching (it would always rebuild).

In the future, we will want to decouple build timestamps from versions.
Remove all instance of overrides_file
Debug logging
Improve logging and documentation for GitCache
Use 40 character left buffer
Don't align output on shasums
Show the list of software names instead of objects
Remove unused Vagrantfile.erb in generator_files
Improve generated omnibus.rb file
Cache the shasum calculation
Add build iteration to `*.metadata.json`

This information is important in various package publishing activities.
Add package_scripts_path as a DSL method
Don't rely on an unreleased version of Ohai [ci skip]