[GEO] Removing unnecessary orientation enumerators

PR #8978 included 4 unnecessary enumeration values ('cw', 'clockwise', 'ccw', 'counterclockwise'). Since the ShapeBuilder.parse method handles these as strings and maps them to LEFT and RIGHT enumerators, respectively, their enumeration counterpart is unnecessary. This minor change adds 4 static convenience variables (COUNTER_CLOCKWISE, CLOCKWISE, CCW, CW) for purposes of the API and removes the unnecessary values from the Orientation Enum.

closes #9035
Fix date histogram docs grammar.
ignore intellij project/workspace files

closes #9044
Search: parse terms filters on a single term as a term filter.

Running a terms filter on a single term is equivalent to loading a postings
list into a bit set and then returning the bit set instead of reading the
postings list on the fly.

Close #9014
Core: Terms filter lookup caching should cache values, not filters.

The terms filter lookup mechanism today caches filters. Because of this, the
cache values depend on two things: the values that can be found in the lookup
index AND the mapping of the local index, since changing the mapping can change
the way that the filter is parsed. We should make the cache depend solely on
the content of the lookup index.

For instance the issue I was seeing was due to the following scenario:
 - create index1 with _id indexed
 - run terms filter with lookup, the parsed filter looks like `_id: 1 OR _id: 2`
 - remove index1
 - create index1 with _id not indexed
 - run terms filter without lookup, the parsed filter is `_uid: type#1 OR _uid: type#2` (the _id field mapper knows how to use the _uid field when _id is not indexed)
 - run terms filter with lookup, the filter is fetched from the cache: `_id: 1 OR _id: 2` but does not match anything since `_id` is not indexed.

Close #9027
Parent/child: Fix concurrency issues of the _parent field data.

`_parent` field data mistakenly shared some stateful data-structures across
threads.

Close #8396
Core: `ignore_unavailable` shouldn't ignore closed indices if a single index is specified in a search or broadcast request.

Closes #9047
Closes #7153
[TESTS] Make sure to wait for all shards to be allocated before running the test.
inner_hits: Added another more compact syntax for inner hits.

Closes #8770
Native: Kernel32Library throws NoClassDefFound if JNA is missing

Introduced by #8993
Doc has store "false" not store "true"

Came from 3465e69e83a4f9f375fb9486741db51efb800837 due to changing "yes" to "false".

Closes #9075
Add index.data_path setting

This allows specifying the path an index will be at.

`index.data_path` is specified in the settings when creating an index,
and can not be dynamically changed.

An example request would look like:

POST /myindex
{
  "settings": {
    "number_of_shards": 2,
    "data_path": "/tmp/myindex"
  }
}

And would put data in /tmp/myindex/0/index/0 and /tmp/myindex/0/index/1

Since this can be used to write data to arbitrary locations on disk, it
requires enabling the `node.enable_custom_paths` setting in
elasticsearch.yml on all nodes.

Relates to #8976
Remove some dead code.
[TEST] Wait for threads to finish / start before asserting