Add pri flag to cat/indices

    % curl localhost:9200/_cat/indices\?h=health,index,rep,docs.count,ss,cs,fm\&v\&pri
    health index   rep docs.count      ss  pri.ss cs pri.cs     fm pri.fm
    green  wiki      1       6401 302.9mb 151.4mb 0b     0b 25.1mb     0b
    green  twitter   1      11434    64mb    32mb 0b     0b     0b     0b