Add GhostBSD definitions of update and upgrades to documentation.

[vimanuelt]

Add GhostBSD definitions of update and upgrades to documentation. Here's an example.

GhostBSD follows its own versioning system (e.g., 2024.10.1), which is independent of FreeBSD's versioning (e.g., 14-STABLE). While GhostBSD may be based on different FreeBSD versions, such as 13-STABLE, 14-STABLE, or later 15-STABLE, its versioning remains distinct. The ghostbsd-version tool provides clarity about the specific FreeBSD version in use.

Upgrades: Typically refer to moving between GhostBSD versions, which may or may not involve a change in the underlying FreeBSD version. For example, upgrading from GhostBSD 2024.07.3 to GhostBSD 2024.10.1 would be considered an upgrade. Transition to a newer release.

Updates: Generally refer to changes within the same GhostBSD version, such as updating ports, applying security patches, or hotfixes. For example, moving from GhostBSD 2024.10.1 to GhostBSD 2024.10.2 would be considered an update. Transition to a newer release.

This distinction should not be confused with pkg terminology:
pkg update refreshes the package repository metadata.
pkg upgrade applies updates to installed packages.

Overall, GhostBSD uses the terms 'upgrade' and 'update' similar to how the Ubuntu and Fedora projects refer to the terms. I suppose that does help Linux users coming to GhostBSD.