elk: add elasticsearch6, logstash6, kibana6 and the beats at v6.1.0

This change is backwards compatible since the ELK tools at version 5.x
remain unchanged.

The test suite now both tests ELK-5 and ELK-6.

pkgs/tools/misc/logstash/6.x.nix

@@ -0,0 +1,39 @@
+{ stdenv, fetchurl, elk6Version, makeWrapper, jre  }:
+
+stdenv.mkDerivation rec {
+  version = elk6Version;
+  name = "logstash-${version}";
+
+  src = fetchurl {
+    url = "https://artifacts.elastic.co/downloads/logstash/${name}.tar.gz";
+    sha256 = "1s2w8d2siryg2wy8i9lwqbp4mjf1sv80lf3sllxwa2vqwsv6l64p";
+  };
+
+  dontBuild         = true;
+  dontPatchELF      = true;
+  dontStrip         = true;
+  dontPatchShebangs = true;
+
+  buildInputs = [
+    makeWrapper jre
+  ];
+
+  installPhase = ''
+    mkdir -p $out
+    cp -r {Gemfile*,modules,vendor,lib,bin,config,data,logstash-core,logstash-core-plugin-api} $out
+
+    wrapProgram $out/bin/logstash \
+       --set JAVA_HOME "${jre}"
+
+    wrapProgram $out/bin/logstash-plugin \
+       --set JAVA_HOME "${jre}"
+  '';
+
+  meta = with stdenv.lib; {
+    description = "Logstash is a data pipeline that helps you process logs and other event data from a variety of systems";
+    homepage    = https://www.elastic.co/products/logstash;
+    license     = licenses.asl20;
+    platforms   = platforms.unix;
+    maintainers = with maintainers; [ wjlroe offline basvandijk ];
+  };
+}