Adds a LocaleProvider enabling custom Locales

The new LocaleProvider can be bound to a custom implementation that
does not necessarily use the browser locale. This is useful if the
Locale should be mapped to a specific value for a custom domain name
for example.
Merge branch 'localeProvider' of github.com:aoiHikari/sitebricks into localeProvider

Conflicts:
	sitebricks/src/main/java/com/google/sitebricks/SitebricksModule.java
	sitebricks/src/main/java/com/google/sitebricks/locale/LocaleProvider.java
	sitebricks/src/main/java/com/google/sitebricks/locale/LocaleProviderImpl.java