Closes #2101 #2092

Renames currentVersion to currentValue, newVersion to newValue, newVersionMajor to newMajor, and newVersionMinor to newMinor.

This PR splits the logic behind changelog into manager (npm) and source (github)
the manager provides the repo url + versions
the source consumes the manager info and generates changelog info

Closes #1911

Refactor changelog (commits) logic to separate sources, and remove the `changelog` dependency. Instead of a full copy/paste of commits, a link is now provided to the source repo.

Closes #381