Multi-locale domain support, fixes #17

[groe]

I have found some time to dig into this :)

This PR fixes sitemaps for craft sites, that have one shared sitemap.xml for multiple locales, i.e. when multiple locales share the same domain. Previously the sitemap would lack <url> tags, as described in #17.

Checking if CRAFT_LOCALE is defined makes sure that single-locale domains are not affected by this change.

[groe]

@joshuabaker If you have any feedback on this, I'm happy to improve it. Let me know what you think.

[groe]

@joshuabaker Have you had time to have a look at it yet?

[jakob-o]

@joshuabaker Hey, is there any chance this will be merged anytime soon?

[stenvdb]

@groe Hi, do you think it's possible when adding custom URL's/routes with the addUrl service method, to add support for multi locale url's as well? I don't see any such option in the plugin at the moment.

I know you're not the main plugin author, but since all last fixes were by you.. Thanks in advance!

[groe]

@Stenvdb Have you tried calling addAlternateUrl on the Sitemap_UrlModel object which is returned from addUrl?

[stenvdb]

@groe Ah, looked over that, works like a charm. Again, thanks!