[EPIC] PHP support

[mscottford]

Build out PHP language support. Initially targeting the support for PHP that existed in freshli-lib (analyzing composer.json and composer.lock).

• Create GitHub repository for freshli-agent-php

(The following issues should be moved to the repository that's created above once it exists.)

• Add skeleton command line application
• Implement detect-manifest
• Implement process-manifest
• Implement validating-repositories
• Implement retrieve-release-history
• Implement validating-package-urls
• Validate against freshli agents verify command

(The following issue should belong to this project)

• Add freshli-agent-php to production docker container image