major rework of backend loading and usage:

- split config from user data to config.json, add config.hson.template
- moved default user data localdb to root folder
- moved pve, localdb, ldap backend handlers to backends sub folder
- add dynamic loading of all backends
- add dynamic mapping for auth backends to support multiple auth sources
- update affected endpoints

src/backends/paasldap.js

@@ -0,0 +1,3 @@
+export default class PAASLDAP {
+
+}