I noticed a couple of inconsistencies when reading through the install bash scripts.
- Make documentation for switches consistent over all files.
- Replace all `sed` implementations of `lowercase` with a more maintainable `tr` implementation.
- Set the `OS` variable in every install script, making it so previously unused checks are actually used.
- Exit with a non-zero exit code when the script reaches an illegal state.
## PR Context
A lot of people, including myself, read the install scripts before executing them. While doing so I noticed they contained inconsistencies. For example, certain flags you can pass to the install script were either undocumented or had an incorrect description. This PR fixes some of these inconsistencies, which should make them easier to maintain and easier to read.
Co-authored-by: Travis Plunk <github@ez13.net>
