Fixed creating server/dist/templates/templates on a 2nd make (#50)

* Fixed creating server/dist/templates/templates on 2nd make

* make the cp switch portable

ref: https://unix.stackexchange.com/questions/18712/difference-between-cp-r-and-cp-r-copy-command

Makefile

@@ -70,7 +70,7 @@ ifneq ($(HAS_SERVER),)
 	cd server && env GOOS=linux GOARCH=amd64 $(GO) build -o dist/plugin-linux-amd64;
 	cd server && env GOOS=darwin GOARCH=amd64 $(GO) build -o dist/plugin-darwin-amd64;
 	cd server && env GOOS=windows GOARCH=amd64 $(GO) build -o dist/plugin-windows-amd64.exe;
-	cd server && cp -r templates dist/templates
+	cd server && cp -R templates dist/
 endif
 
 # webapp/.npminstall ensures NPM dependencies are installed without having to run this all the time