Remove Lucene's deprecated PatternTokenizer

Instead of using the PatternTokenizer, the functionality was replicated by using Lucene's StopFilter, PatterTokenizer and LowerCaseFilter

Closes #6717
Add v1.2.3 to Version.java
Fix typo in Hunspell logging
Docs: Update plugins.asciidoc

Closes #6683
Docs: New entry/front-end

Adding, Calaca, a simple search client for Elasticsearch.

Closes #6754
[Test] BackgroundIndexer uses the wrong logger

Closes #6781
Merge pull request #6792 from areek/fix/6717

Remove Lucene's deprecated PatternAnalyzer
Upgrade to jackson core 2.4.1.1
Note, we had to disable the symbol overflow, since the many mapping case was tripping it
closes #6789
Modify command window title (windows)

When launching multiple nodes in MS Windows env, batch command window does not come by default with any title.

This patch add `Elasticsearch VERSION` as a title, where VERSION is the current elasticsearch version.

Same for `plugin.bat` and `service.bat`.

Closes #6336
Closes #6752
[TEST] move more tests to assertBusy from awaitBusy
Disable JSONP by default
By default, disable the option to use JSONP in our REST layer
closes #6795
Improve large bytes request handling by detecting content composite buffer
There is a special type of request that tries to not allocate another buffer when sending bytes request (used by the public cluster state action). With the new pages bytes reference support, the content can already be a composite channel buffer, take that into account when building the actual composite buffer that will be sent over the network
closes #6756
Enables plugins to define default logging configuration for their needs.

- adds support for multiple logging configurations under the config dir (will pick up any logging.xxx in the config folder tree)
- plugins can now define a top level config directory that will be copied under es config dir and will be renamed after the plugin name (same as the support we have the plugin "bin" dirs)

 Closes #6802
[TEST] make completion tests more resilient to delayed mapping
especially the tests that check for update of mapping, we need to make sure that the cluster is green so mappings won't get override, also, put mapping during index creation when possible
[TEST] relax size test, to not run into OOM
Added a check on moving bin & config plugin dirs

Plugins can contain bin & config sub-dirs that are copied to es's bin & config directories. If moving these directories fails we now throw an error.
[TEST] SuppressSysoutChecks on ElasticsearchPostingsFormatTest
[TEST] Mute PluginManagerTests#testLocalPluginInstallWithBinAndConfig
[STORE] Make a hybrid directory default using `mmapfs` and `niofs`

`mmapfs` is really good for random access but can have sideeffects if
memory maps are large depending on the operating system etc. A hybrid
solution where only selected files are actually memory mapped but others
mostly consumed sequentially brings the best of both worlds and
minimizes the memory map impact.
This commit mmaps only the `dvd` and `tim` file for fast random access
on docvalues and term dictionaries.

Closes #6636
[ENV] Release node env if initialization fails

If the node initialisation fails, make sure the
node environment is closed correctly and thus
all locks (on data directories) being properly released.

Closes #6715