key is "index.store.type", not "index.storage.type"
Plugin Manager should support -remove group/artifact/version naming
When installing a plugin, we use:

```sh
bin/plugin --install groupid/artifactid/version
```

But when removing the plugin, we only support:

```sh
bin/plugin --remove dirname
```

where `dirname` is the directory name of the plugin under `/plugins` dir.

Closes #3421.
Catch ESRejectedExecutionException on node close

When a node shuts down thread pools might throw
ESRejectedExecutionException and our test framework fails tests if
exceptions are not caught hitting uncaught exception handler.
Rename IndexShard#searcher() to #acquireSearcher()

Based on recent bugs ( #3652 ) where searchers were acquired multiple times
but never released 'IndexShard#searcher()' has not a more accurate name.

Closes #3653
use ElasticsearchAssertions to get info on shard failures
Configured TRACE logging to RecoveryWhileUnderLoadTests#recoverWhileUnderLoadAllocateBackupsTest

We want to log which shards we are searching on and which shards we are refreshing
change logging level of testTimeoutSendExceptionWithDelayedResponse to TRACE
Plugin Manager: add silent mode.
Now with have proper exit codes for elasticsearch plugin manager (see #3463), we can add a silent mode to plugin manager.

```sh
bin/plugin --install karmi/elasticsearch-paramedic --silent
```

Closes #3628.
Added clear scroll api.

The clear scroll api allows clear all resources associated with a `scroll_id` by deleting the `scroll_id` and its associated SearchContext.

Closes #3657
Rewrote SuggestResponse#toString method

It only prints out json now (as the SearchResponse does)
Added missing startObject & endObject (was causing JsonGenerationException)

Closes #3661
Add support for Lucene's MockDirectoryWrapper

MockDirectoryWrapper adds asserting logic to the low level directory
implementation that helps to track and catch resource leaks like
unclosed index inputs caused by dangling IndexReader or IndexSearcher
instances. It prevents double writes to files and allows low level
random exceptions to be thrown for testing index consistency etc.

Closes #3654