added rake task for adding NilmDB nodes

lib/tasks/nilm.rake

+require 'factory_bot_rails'
+
+namespace :nilm do 
+  desc "Add a nilmdb database"
+  task :add, [:email, :name, :url] => [:environment] do |t, args|
+    adapter = Nilmdb::Adapter.new(args[:url])
+    service = CreateNilm.new(adapter)
+    service.run(name: args[:name], url: args[:url],
+                owner: User.find_by_email(args[:email]))
+    if service.success?
+      puts "created Nilm #{args[:name]} with owner #{args[:email]}"
+    else
+      puts args.warnings
+      puts args.errors
+    end
+  end
+end
+