[DOCS] Add X-Pack license settings (elastic/x-pack-elasticsearch#2833)

Original commit: elastic/x-pack-elasticsearch@6bab830682

docs/en/settings/configuring-xes.asciidoc

@@ -3,6 +3,7 @@
 == Configuring X-Pack
 
 include::x-pack-settings.asciidoc[]
+include::license-settings.asciidoc[]
 include::ml-settings.asciidoc[]
 include::monitoring-settings.asciidoc[]
 include::security-settings.asciidoc[]

docs/en/settings/license-settings.asciidoc

@@ -0,0 +1,19 @@
+[role="xpack"]
+[[license-settings]]
+=== {xpack} License Settings
+++++
+<titleabbrev>License Settings</titleabbrev>
+++++
+
+You can configure this licensing setting in the `elasticsearch.yml` file.
+For more information, see
+{xpack-ref}/license-management.html[{xpack} License Management].
+
+`xpack.license.self_generated.type`::
+Set to `trial` (default) to enable all {xpack} features. +
++
+--
+If set to `basic`, the self-generated license gives access only to the features
+of a standard basic license. You can later upgrade the cluster to a trial
+license.
+--

docs/en/settings/x-pack-settings.asciidoc

@@ -12,3 +12,6 @@ You configure settings for X-Pack features in the `elasticsearch.yml`,
 |Security          |{ref}/security-settings.html[Yes]      |{kibana-ref}/security-settings-kb.html[Yes]   |No
 |Watcher           |{ref}/notification-settings.html[Yes]    |No                                  |No
 |=======================
+
+There are also {ref}/license-settings.html[{xpack} license settings] in the
+`elasticsearch.yml` file.