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.
Move systemd files from /etc to /usr/lib

As documented in systemd's manual pages tmpfiles.d(5) and systemd.unit(5),
a package should install its default configuration in /usr/lib, which can
be overriden by system administrators in /etc.

New locations in the rpm:
/usr/lib/systemd/system/elasticsearch.service
/usr/lib/tmpfiles.d/elasticsearch.conf
cleanup formatting in significant aggs package
[TEST] Print tests.jvms and tests.client.ratio if set

We need to print options that can modify stream of events we need
to print it otherwise a seed might not reproduce the failure in
the tests.
[DOCS] Add Azure storage repositories
[TEST] pre check download service working

Seen during CI tests, it could appears that the download service is not available for any reason.

This fix in test will check before each test which requires an internet access (annotated with @Network) that the download service we are testing is still working.

It won't fail the test but will mark the test as `Ignored` in case of failure.
Findbug warning supression

Added logic to enable findbug warnings supression via annotations
Revert "Findbug warning supression"

This reverts commit 744eabad030f8f8c5705beeea7ab7eeb47f84969.
Add ability to get snapshot status for running snapshots

Closes #4946
Made p/c override the clone() method. This is necessary since by default clone will make a shallow copy of the original object, while for p/c queries we need to make sure that the wrapped queries are also cloned.