[DOCS] Documented gateway.local.auto_import_dangled

Relates to #4996
BulkProcessor process every n+1 docs instead of n

When you set a BulkProcessor with a bulk actions size of 100, it executes the bulk after 101 documents.

```java
BulkProcessor.builder(client(), listener).setBulkActions(100).setConcurrentRequests(1).setName("foo").build();
```

Same for size. If you set the bulk size to 1024 bytes, it will actually execute the bulk after 1025 bytes.

This patch fix it.

Closes #4265.
[Tests] RecoveryWhileUnderLoadTests - made sure background indexing threads are closed on errors.

Fixed minor logging discrepancies introduced with randomized shard count.
Added logging to recoverWhileUnderLoadWithNodeShutdown
Added logging ElasticsearchIntegrationTest.allowNodes to indicate what nodes were excluded.
recoverWhileRelocating's shard setting were potentially ignored (depending on key order in hashmaps)
[TEST] add mapping to MoreLikeThisActionTests to make sure doc mapper exists on all shards / nodes
Add _cat/plugins endpoint

If we want to have a full picture of versions running in a cluster, we need to add a `_cat/plugins` endpoint.

Response could look like:

```sh
% curl es2:9200/_cat/plugins?v
node component                        version   type url                                   desc
es1  mapper-attachments               1.7.0       j                                        Adds the attachment type allowing to parse difference attachment formats
es1  lang-javascript                  1.4.0       j                                        JavaScript plugin allowing to add javascript scripting support
es1  analysis-smartcn                 1.9.0       j                                        Smart Chinese analysis support
es1  marvel                           1.1.0      j/s http://localhost:9200/_plugins/marvel Elasticsearch Management & Monitoring
es1  kopf                             0.5.3       s  http://localhost:9200/_plugins/kopf   kopf - simple web administration tool for ElasticSearch
es2  mapper-attachments               2.0.0.RC1   j                                        Adds the attachment type allowing to parse difference attachment formats
es2  lang-javascript                  2.0.0.RC1   j                                        JavaScript plugin allowing to add javascript scripting support
es2  analysis-smartcn                 2.0.0.RC1   j                                        Smart Chinese analysis support
```

Closes #4824.
Count latch down if sendsPing throws exception

if the async sendPingsHandler throws an unexpected exception the
corresponding latch is never counted down. This might only happen
during node shutdown but can still cause starvation or test failures.
MulticastChannel returned wrong channel in shared mode

If the shared channel is used a wrong refrence was returned and
close calls couldn't find the listener since it go never registered
in that instance.
[TEST] Make sure that the facet fields exist.
[TEST] In PercolatorTests#testPercolateSorting_unsupportedField we need to be sure that the .percolator type exists
Enforce java version 1.7

When building elasticsearch, we now require to use java 1.7.

Maven will check that before compiling any class. If Java version is incorrect, you will get the following message:

```
[WARNING] Rule 0: org.apache.maven.plugins.enforcer.RequireJavaVersion failed with message:
Detected JDK Version: 1.6.0-65 is not in the allowed range [1.7,).
```

Closes #5428.
[Test] IndexLifecycleActionTests - set minimum master node earlier to make sure it's in effect when needed.
[Test] FullRollingRestartTests - correctly setting minimum_master_nodes

Also added a ElasticsearchIntegrationTest.setMinimumMasterNodes() helper function.
[Tests] QuorumLocalGatewayTests - Set mini_master_nodes earlier to make sure it has effect.  ClusterServiceTests - remove a thread.sleep in favor of awaitBusy
[Docs] added a missing reference to significantterms-aggergations

Also fix header level mismatch issue reported by the build
[DOCS] Updating scripting docs for geo functions

Added a few functions are corrected the default unit where necessary
[DOCS] Fix typo in the reference doc. SuSe -> SUSE

SUSE, as a Linux distribution, is never lower cased

fixes #5354
[DOCS] Reword clear-scroll sentence
[DOCS] Fixing contributing.md indentation

Add a whitespace to make these separate paragraphs inside of a list.
Documentation fix for significant_terms heading levels
[TEST] Use client node such that we always have to do a round-trip to do a fetch.