Implement plugin manifest parsing

[patrickjcasey]

Implement parsing logic found in https://github.com/mitre/hipcheck/blob/main/site/content/rfds/0004-plugin-api.md for plugin manifest.

Example:

publisher "mitre"
name "affiliation"
version "0.1.0"
license "Apache-2.0"
entrypoint {
  on arch="aarch64-apple-darwin" "./hc-mitre-affiliation"
  on arch="x86_64-apple-darwin" "./hc-mitre-affiliation"
  on arch="x86_64-unknown-linux-gnu" "./hc-mitre-affiliation"
  on arch="x86_64-pc-windows-msvc" "./hc-mitre-affiliation"
}

dependencies {
  plugin "mitre/git" version="0.1.0" manifest="https://github.com/mitre/hipcheck/blob/main/plugin/dist/mitre-git.kdl"
}

[patrickjcasey]

closed by #293