Nicer failure message when node should not connect to another in nodes API
There are cases where nodes should not connect to another node. For example, client nodes do not connect to other client nodes. When executing a nodes level API, we should have a nicer failure indicating that, and not log it by default, as its not a real failure
Added support for aliases to index templates

Adapted existing PR (#2739) to updated code (post #4920), added tests and docs (@javanna)

Closes #1825
Improved how aliases get parsed in create index

Added also CreateIndexRequest#aliases(BytesReference) method
[TESTS] Fixed YAML in put_templates test
Added support for char filters in the analyze API

Closes #5148
[TEST] removed explicit index deletion from AnalyzeActionTests, more ensureGreen
since we no longer have bytebuffer dir, this test is not needed
Introduced a new IMMEDIATE priority - higher than URGENT

* applied to cluster update settings, reroute, node join/leave events, node failure

Closes #5062