Order unspecified properties at the end

Previously the `SortedProperties` linter would prefer unspecified
properties to be ordered at the beginning. Since this doesn't really
align with the purpose of specifying an explicit order, change it to
order them at the end.

Change-Id: I168517747c1391055626b2d3da6650df54b64e09
Reviewed-on: http://gerrit.causes.com/36070
Tested-by: jenkins <jenkins@causes.com>
Reviewed-by: Shane da Silva <shane@causes.com>