use more aggressive concurrency levels for CHM
- long running ones with high update rates
- also expose a *system* property of es.useConcurrentHashMapV8 to use the new non blocking Java8 CHM impl
If a value/field is a Calendar, it will be converted to a Date using getTime()
Closes #2911
# Response for Cluster Settings Update API

If cluster settings are update the REST API returns the accepted values. For
example, updating the `cluster.routing.allocation.disable_allocation` via
cluster settings:

```curl -XPUT http://localhost:9200/_cluster/settings -d '{
    "transient":{
        "cluster.routing.allocation.disable_allocation":"true"
    }
}'```

will respond:

```{
    "persistent":{},
    "transient":{
        "cluster.routing.allocation.disable_allocation":"true"
    }
}```

Closes #2907
make object caching optional
allow CacheRecycler to be cleared via the REST API
s/ES.RECYCLE/es.cache.recycle
remove size bound from cache recycler for performance reasons
Support empty string in FSTBytesAtomicFieldData
Apply minimum_should_match to inner clauses of multi_match query
When specifying minimum_should_match in a multi_match query it was being applied
to the outer bool query instead of to each of the inner field-specific bool queries.

Closes #2918
Added tests for multi_match with minimum_should_match
use Double/Float.compare for stable and correct float sort order
Added more test assertions
Remove per-doc ord collector callback infavor of an iterator
Cut over StringScriptDataComparator to use BytesRef instead of Strings

Closes #2920
Fall back to local statistics if global statistics are not availalbe for a field or term

Closes #2926
If searchContext not set, abort parsing and throw ISE
Fix serialization of sync/async replication type
no longer support snappy...
Added stolen time to OsStats output
Fixing possible NoClassDefFoundError when trying to load nonexisting classes

In order to handle exceptions correctly, when classes are not found, one
needs to handle ClassNotFoundException as well as NoClassDefFoundError
in order to be sure to have caught every possible case. We did not cater
for the latter in ImmutableSettings yet.

This fix is just executing the same logic for both exceptions instead of
simply bubbling up NoClassDefFoundError.