Reading wikipedia

This commit contains basic tools to load Wikipedia graph to Cassovary:

1. RedirectsExtractor - tool to parse Wikipedia dumps and get all redirects to a single file.
2. DumpToGraphConverter - tool to parse Wikipedia dumps and print links graph as adjacency list for Cassovary
3. HashMapsBasedWikipediaGraph - classes that read Wikipedia graph and redirects from previous tools and store them in a graph and hash table.

Using this code it's possible to load Wikipedia to Cassovary. Steps take following times (on server class machine):
1. Redirects - 2000s
2. Dumps to Graph - 1800s
3. Reading - 304 s.
don't know how big the strings are, but can think of putting these not in an memory map but in an embedded DB like Mapdb or in an sstable