Each package should have a dedicate changelog in it's directory as a seperate file. The name of the changelog could be packagename.changelog. Thus for example, the '/usr/portage/dev-db/postgresql' directory contains the '/usr/portage/dev-db/postgresql/postgresql.changelog' file. The changelog format could be similar to the portage changelog.
Change it to "ChangeLog", other than that I agree.
Generated all initial changelogs and an example skel.ChangeLog. Drobbins is posting an announcement on the mailinglists.