Adds first draft to configure regular expressions for a wikipedia dump.

Hi knutwalker,
would you be so kind to take a minute to review these changes so we can prepare this change for the public.

I was actually thinking of `org.elasticsearch.common.collect.ImmutableMap.copyOf(languagePattern)` [instead of an unmodifiable](http://stackoverflow.com/a/8892376/2996265) but I guess my comment got lost due to a shitty mobile network...
Anyway, since this map is only used in the constructor of `WikiTextParser`, and the owner of the map does make arbitrary modifications possible, it doesn't really make any difference if this is immutable, unmodifiable, or something else. Didn't get the bigger picture on the car drive. Sorry for the hustle :)