* Create asdf-version script to print formatted version
* Update Makefile to set main.version variable during build
* Improve help output formatting
* Update release-build workflow to set asdf version in binaries
* Switch to non-verbose test output in Makefile
* Create pluginindex package with PluginIndex struct with methods for updating index and retrieving plugin URLs
* Create IndexRepo interface to allow for easy testing out cloning real Git repository.
