Enhancement: Implement semantic versioning

MC has been updated and extended in a variety of ways, but the versioning used does not communicate what version one might need in any consistent way. Since MC is intended to frequently be used from scripts or other software, it's important to know when things change. Moving forward, I'd like to see reasonable adherence to semantic versioning (https://semver.org/).

For the purposes of MC, I would consider it important to increment the major number any time:
* handling of existing command line arguments is changed (including ones added since the last major release)
* existing output formats are modified (e.g. changes are made to how multiline messages are printed to STDOUT)

Changing these things can break an existing script that uses MC, and that should be apparent just by the version number. It can feel a little weird to increase the major version number when all you did was tweaked the way you indent JSON output or something, but from the perspective of someone writing code that relies on knowing the behavior of MC, it's pretty important.