Fix behavior of group "exclude" options

[ecraig12345]

Currently the exclude option for ChangelogGroupOptions and VersionGroupOptions (and isPathIncluded internally) expects negated patterns: e.g. if you want to exclude packages/foo, you must specify exclude as !packages/foo.

This is a counterintuitive design which does not match other tools, and should be updated in a major version to remove the negation requirement.