Define some constants in a single place, while avoiding a cyclical
import dependency issue.
Cannot reference the constants defined in supersede directly from a
class in searchers since supersede already imports a class in
searchers and doing an import of supersede into searchers results in a
cyclical dependency.
Instead move these out to a common file in the module as constants.
Change-Id: I350ba85f8af90cefe42fa497f88591f1e88d8d07
754db13543