*find_package* for python modules

include(PythonPackage)
find_python_package(<NAME>
   [REQUIRED]        -- will fail if package not found
   [VERSION version] -- minimum version
   [EXACT]           -- must find exact version
   [QUIET]           -- silence is golden
)

Sets ${NAME}_FOUND, as well as ${NAME}_LOCATION containing the directory where the module resides, and ${NAME}_VERSION_STRING the version of the package.