Restore JDK 1.6 compatibility in PluginsUtils

Jar/ZipFile do not implement Closable in JDK 1.6 (only in 1.7)
[TEST] Add version and master_node parameter to _cluster/state
[TEST] Dynamically extract node ID for test
fix failing IsolatedPluginTests (change numNodes to 0)
[DOCS] Fixed added[] tag version number
Fix backwards compatibility for cluster state REST response
[TEST] skip explain reroute REST test until param substitution is implemented
Remove same-thread checks when recycling (see #5254).
Prevent page-tracking checks from spreading across tests.
Reuse pages more agressively in BigArrays.

Pages are now going to be reused when the size of the array is greater than
${page_size}/2 (as opposed to ${page_size} currently).

Close #5299
fix issues in IsolatedPluginTests running on CI (relative assertations)

relates to #5621
fix typo causing incorrect plugin properties lookup in jars

relates to #5261
[TEST] added support for replacing stashed values within objects and lists in our REST tests
[TEST] re-enabled cluster.reroute/11_explain test that requires unstashing values within objects
[DOCS] Better document the limitation of nested objects.
Percentiles aggregation.

A new metric aggregation that can compute approximate values of arbitrary
percentiles.

Close #5323
Fix test bug: a too low compression level can make accuracy terrible.
Clarify range aggregations
[DOCS] Java API JSON typo
Terms aggs: only use ordinals on low-cardinality fields by default.

Close #5303