Completion postings format: Write hole character

Another issue found by randomized testing.
Refactored put mapping api to make use of the new recently introduced generic ack mechanism

Note: we were previously waiting for ack only from all nodes that contain shards for the indices that the mapping updatewas applied to. This change introduces a wait for ack from all nodes, consitent with other api as the ack is meant more on the cluster state itself, which is held by all nodes and needs to be updated on all nodes anyway.

Closes #4228
- Added docs for the value_count aggregation
- Fixed typos in the terms facets docs
- Fixed aggregation docs layout
- Added docs for shard_size in term aggregation
- Added support for term filtering based on include/exclude regex on the terms agg
- Added javadoc to the TermsBuilder

Closes #4267
fixed typo in TestCluster
test classes cleanup (fixed warnings and typos)
Add line feed for prettified main REST action
Fix computation of explanations for AllTermQuery.

The use of freq() instead of sloppyFreq() and the fact that `numMatches` was
not updated in `setFreqCurrentDoc` could lead to an inaccurate score in the
explanation.

Close #4298
Changed the minScore comparator from > to >=

Closes #4303
Added simple test for minScore
trimmed down SimpleQueryTests + more assertAcked
NullPointerException in FsTranslog when reverting transient log
This happens when reverting the trans transaction log on failure, and when that happens, actually we might have failed on the transient translog creation to being with....
fixes #4223
added assertions for shard failures in stats agg tests
added more assertions to aggs tests
Cat API: Improve help and execute help before sending server requests

* Force the cat API classes to have simple help available by extending from a AbstractCatAction
* Use a set binder on guice creation to create the help on node start up
* Make sure that the help/field info is returned without querying any data
wait for green in tests for now
Fixes related to accepted docs not taken into account:
* Removed the applyAcceptedDocs in ChildrenConstantScoreQuery, they need to be applied at all times. (because of short circuit mechanism)
* Moved ParentDocSet to FilteredDocIdSetIterator, because it fits better than MatchDocIdSet.
* Made similar changes to ParentConstantScoreQuery for consistency between the two queries. The bug accepted docs bug didn't occur in the ParentConstantScoreQuery.
* Updated random p/c tests to randomly update parent or child docs during the test run.

Closes #4306
Also short circuit within segment when score mode is avg
Make the ChildrenQuery and ParentQuery not rely on the fact that score of 0 means that there isn't a match.
add more ensureGreen to aggs tests