BaseCmdPkgRelations contains pkg_relations(), a function doing
package graph analysis code. The function needs to be made available
to code outside BaseCmdPkgRelations, so move it to
cmds.projects.lib.pkg_relations.
The commit also applies style fixes to both BaseCmdPkgRelations and
pkg_relations which anticipate broader style changes to jw-pkg in
general.
Signed-off-by: Jan Lindemann <jan@janware.com>