Allow negative slops in SpanNearQueryParser

This is mainly due to the fact that SpanNearQuery allows some neat
tricks with negative slops to run zero-sloped near queries across
2 or more SpanTermQueries.

Closes #3079
Improve integration testing by reusing an abstracted cluster across tests

The new AbstractSharedClusterTest abstracts integration testing further to
reduce the overhead of writing tests that don't rely on explict control over
the cluster. For instance tests that run query, facets or that test highlighting
don't need to explictly start and stop nodes. Testing features like the ones
just mentioned are based on the assumption that the underlying cluster can
be arbitray. Based on this assumption this base class allows to:

 * randomize cluster and index settings if not explictly specified
 * transparently test transport & node clients
 * test features like search or highlighting on different cluster sizes
 * allow reuse of node insteance across tests
 * provide utility methods that act as upper or lower bounds that a test must pass with
   ie. if a test requries at least 3 nodes then it should also pass with 4 nodes
 * given a cluster has unmodified cluster settings (persistent and transient) the cluster
   should not differ to a fresh started cluster when reused across nodes.
 * within a test the client implementation and the clients associated node can be changed
   at any time and should return a valid result.

This patch also prepares some redundant tests like 'RelocationTests.java' for randomized
testing. Test like this are very long-running on some machines and run the same test with
different parameters like 'number of writers' or 'number of relocations' which can easily
be chosen with a random number and run only ones during development but multiple times
during CI builds.

All the improvements in this change reduce the test time by ~30%
Ensure config files are not overwritten in RPM upgrade

In order to ensure that configuration files do not get overwritten when
upgrading an RPM, it is not sufficient to mark them as configuration. You
have to use the 'noreplace' parameter to make sure, they are never
overwritten. Added this parameter for the /etc/elasticsearch directory
as well as the /etc/sysconfig/elasticsearch file.

In addition, the post remove script now only deletes the user in case of
a package removal (and does nothing on package upgrade).

Closes #3123
Add Test for simple allocation scenario

This test checks for the "perfect" or a "sane" allocation
when the total number of shards is separable by the total number of nodes
the index can be allocated on.
Stableize SearchStatsTest after search refactoring

SearchStatsTest depends on a given set of nodes and shards. The test
needed to be adjusted to reflect a possibly random number of nodes.
Stabelize MoreLikeThisActionTest

Ensure test sends mapping with createIndex
stabelize SimpleQueryTest
Changing version semantics to be more readable

The Version class had hard to understand semantics when two versions were
compared against each other.

Sample of the new logic:
* V_0_20_0.before(V_0_90_0) => true
* V_0_90_0.after(V_0_20_0)  => true

Closes #3124
Changed Java dependency from Depends to Suggest.

Since people are using the Oracle JAVA distribution and not the OpenJDK.
You can suggest it of course. Now the installation will at least continue.

If the init script is called, it will exit with a useful error message, that
no JDK is available via the JAVA_HOME variable.
Stabeilze SearchStatsTests

Query stats are only present (not 0) on nodes that hold a shard of the index.
Fix AbstractSimpleEngineTests versioning tests.

Version is now stored on a distinct field, that AbstractSimpleEngineTests
didn't correctly add before running tests. This generated a test failure
when the version needed to be loaded from the index.
Stabelize more failing tests.

- SimpleSortTests#testSortScript which was not using the mapping correctly
- SearchStatsTests#testSimpleStats which didn't clear the stats before
  running the test and a previous run could have added queries
Fix SearchStatsTest

Use actual node in test instead of the first node in the array
More test cleanups
Fixed `has_parent` query and filter returning no results with multi level child docs.
Added a benchmark for parent/child queries while indexing at the same time.
report details if shard response has failed shards
Correct offsets in FVH also if stored field is used for highlighting

The SimpleFragemntsBuilder did not correct offsets if the used
analysis chais could produce broken offsets that could lead to
StringArrayIndexOutOfBounds Exceptions

Closes #3140
Fallback to extract terms if MultiPhraseQuery is large

Currently if MPQ is very large highlighing can take down a node
or cause high CPU / RAM consumption. If the query grows > 16 terms
we just extract the terms and do term by term highlighting.

Closes  #3142 #3128
Stabelize more tests

Wait for relocation before checking statistics or run refresh / optimze.