indexer: Initial cosine search implementation
Improve output format for search

This is still WIP but matches the TREC file.
search: Don't restrict to newsgroup
Style fix
indexer: Make stemming optional and use the flag for the search
Merge branch 'master' into task_12
indexer: Pass the stemming boolean down from main
indexer: Cleanups
Move search call to main

Call get_similar_documents directly from main.