Allow choosing the translation in the .properties file.

Allow choosing the translation in the .properties file.

	* src/main/java/org/glom/web/server/OnlineGlomServiceImpl.java
	init(): Read a glom.document.locale value from the configuration file
	and call Glom's TransatableItem::set_current_locale() method.
	* src/main/resources/onlineglom.properties: Add a commented-out
	example of this new setting.

	It would be better to add &lang=de_DE to the URL, but the current
	libglom API does not allow us to do this easily. I am working on that.