Makes sure all POMs contain a description

[colings86]

Also adds an explicit description the RPM package so it doesn't inherit the description from the POM.

Closes #12550

[spinscale]

Debian package:

# dpkg --info deb/target/releases/elasticsearch-2.0.0-beta1-SNAPSHOT.deb
...
Description: Open Source, Distributed, RESTful Search Engine
  Elasticsearch is a distributed RESTful search engine built for the cloud.
  .
  Features include:
  .
  + Distributed and Highly Available Search Engine.
    - Each index is fully sharded with a configurable number of shards.
    - Each shard can have one or more replicas.
    - Read / Search operations performed on either one of the replica shard.
  + Multi Tenant with Multi Types.
    - Support for more than one index.
    - Support for more than one type per index.
    - Index level configuration (number of shards, index storage, ...).
  + Various set of APIs
    - HTTP RESTful API
    - Native Java API.
    - All APIs perform automatic node operation rerouting.
  + Document oriented
    - No need for upfront schema definition.
    - Schema can be defined per type for customization of the indexing process.
  + Reliable, Asynchronous Write Behind for long term persistency.
  + (Near) Real Time Search.
  + Built on top of Lucene
    - Each shard is a fully functional Lucene index
    - All the power of Lucene easily exposed through simple
      configuration/plugins.
  + Per operation consistency
    - Single document level operations are atomic, consistent, isolated and
      durable.
  + Open Source under the Apache License, version 2 ("ALv2").
 Homepage: https://www.elastic.co/

and the RPM

# rpm -pqi rpm/target/releases/elasticsearch-2.0.0-beta1-SNAPSHOT.rpm
Name        : elasticsearch                Relocations: /usr
Version     : 2.0.0                             Vendor: (none)
Release     : beta1_SNAPSHOT20150810122129   Build Date: Mon Aug 10 14:22:02 2015
Install Date: (not installed)            Build Host: orca.fritz.box
Group       : Application/Internet          Source RPM: elasticsearch-2.0.0-beta1_SNAPSHOT20150810122129.src.rpm
Size        : 32332940                         License: (c) 2009
Signature   : RSA/SHA1, Mon Aug 10 14:22:02 2015, Key ID c4afd48faa37d761
Packager    : Elasticsearch
Summary     : Elasticsearch RPM Distribution
Architecture: noarch
Description :
Open Source, Distributed, RESTful Search Engine Elasticsearch is a distributed RESTful search engine built for the cloud.

The RPM description is kind of repeating itself in the two sentences?

minor thing: maybe unify the description between both packages, and have the RPM summary return s/Distribution/Package?

LGTM other than that

[spinscale]

LGTM