Make settings in .ini optional and add new ones

Fixes #24

New settings available :
STATIC_ROOT
STATIC_URL
LANGUAGE_CODE
TIME_ZONE

etesync-server.ini.example

@@ -1,6 +1,11 @@
 [global]
 secret_file = secret.txt
 debug = false
+;Advanced options, only uncomment if you know what you're doing:
+;static_root = /path/to/static
+;static_url = /static/
+;language_code = en-us
+;time_zone = UTC
 
 [allowed_hosts]
 allowed_host1 = example.com