Feat/package cxx

[lwbuchanan]

Automatically installs cxxbridge-cmd to the megaton home if not already installed

Uses cargo-metadata to make sure that cxx is included in the root crate package and the semver doesn't allow for versions outside of the 'blessed' version

[lwbuchanan]

This is checking the wrong version data. It should check the actual installed version of cxx, not the req from the manifest.

[lwbuchanan]

Fixed the version check, but i noticed that cargo now takes longer to run after getting the metadata. Without the cxx version check, megaton build takes ~0.13s if nothing needs built. Now it takes ~0.35s. It seems like cargo build runs for a little bit longer if cargo metadata has been run since the last build. Not sure if this is a significant issue, but its a bit annoying so just mentioning in case anyone knows of a fix for this.