Refactor how properties files are read from server

[elmasse]

We should load the files in the following order:

Application.properties
Application_xx.properties //1
Application_xx-YY.properties //2

1 if lang is specified as 'xx' or 'xx-YY' (for instance: 'en', 'en-US');
2 if lang is specified as 'xx-YY'

Load order should be reversed as from today. Load the bottom-up from less to more specific and override the keys.