relocate repo files so ND2 is the only code

lib/App/Netdisco/DB/ResultSet/Subnet.pm

@@ -0,0 +1,11 @@
+package App::Netdisco::DB::ResultSet::Subnet;
+use base 'App::Netdisco::DB::ResultSet';
+
+use strict;
+use warnings;
+
+__PACKAGE__->load_components(qw/
+  +App::Netdisco::DB::ExplicitLocking
+/);
+
+1;