Locale dependent default settings

[Chocimier]

In discussion on #778, @Emdek mentioned about needed "mechanism to set defaults depending on locale".
This can be achieved in way it works in Opera extensions: there is a folder with global defaults (existing now one) and subfolders named same as locale containing additional local defaults.
There should be way to both join or replace global values with local.
We can also use a "dynamic" pseudo-locale to generate locale setting dynamically, like locale search engines, differing only with subdomain in address.
Also user profile should allow to use this mechanism, but without GUI for this feature.

[Chocimier]

We can also use it to provide platform-dependent settings, it will solve problems like #844.