[mail_templates]:

[Upd] Mail
--> Improved Mail.init. You have to provide a config now.
--> Added template support (with caching)
--> Fixed wrong property access on the client object.
--> All methods implemented with promises.
[Upd] Config
--> Improved usage using promises.
--> The ssl credentials are loaded together with the config file now.
[Upd] Database::User
--> All mail functions are using promises instead of callbacks.
--> Asserts that the config is loaded (@require)
[Upd] Server
--> Asserts that the config is loaded (@require)
[Upd] Middleware
--> Asserts that the config is loaded (@setupHttpsMiddleware)
Merge branch 'mail_templates' into dev