Allow to change concurrent merge scheduling setting dynamically
Allow to change the concurrent merge scheduler settings dynamically using the update settings API
closes #6098
[TESTS] Improve BenchmarkIntegrationTest's check that percentiles are increasing.

Percentiles are supposed to be monotonically increasing but floating-point
rounding issues can come into play and make the test fail if checks are too
strict.
Check if root mapping is actually valid

When a mapping is declared and the type is known from the uri
then the type can be skipped in the body (see #4483). However,
there was no check if the given keys actually make a valid mapping.

closes #5864
closes #6093
5882: put back Elasticsearch's 1.1 defaults for ConcurrentMergeScheduler
#6120 Remove SerialMergeScheduler (master only)

It's dangerous to expose SerialMergeScheduler as an option: since it only allows one merge at a time, it can easily cause merging to fall behind.

Closes #6120
#5882: fix docs
#6081: set IO throttling back to 20 MB/sec now that #6018 is fixed
Change key to keyed
fixed MetaData#concreteIndices to throw exception with a single index argument in case allowNoIndices == false and ignoreUnavailable == true

Closes #6137
improved IndicesOptions javadocs
Fix for benchmark test timeout

Lower number of random requests generated for each test so as not to
timeout on heavy tests.

Addresses #6094
Fix for hanging aborted snapshot during node shutdown

If a node is shutdown while a snapshot that runs on this node is aborted, it might cause the snapshot process to hang.

Closes #5958
[DOCS] Added "Aggregation" to all aggs titles
Log script change/add and removal at INFO level

Closes #6104
Significant_terms agg: added option for a background_filter to define background context for analysis of term frequencies

Closes #5944
[DOCS] Fix typos in context suggest
Use t-digest as a dependency.

Our improvements to t-digest have been pushed upstream and t-digest also got
some additional nice improvements around memory usage and speedups of quantile
estimation. So it makes sense to use it as a dependency now.

This also allows to remove the test dependency on Apache Mahout.

Close #6142
[TEST] Changed the possessive matching syntax in cat.recovery
regex to use an independent subexpression. Possessive
modifiers not supported on older Perl
[DOCS] Changed coming[1.1.0] to added in snapshot status
[JAVADOCS] Fix wrong javadoc in IdentityHashSet.

Close #6121