Restructure documentation

Signed-off-by: Roberto Rosario <roberto.rosario@mayan-edms.com>

docs/chapters/languages.txt

@@ -0,0 +1,36 @@
+=========
+Languages
+=========
+
+The list of languages choices in the language dropdown used for documents is
+based on the current ISO 639 list. This list can be quite extensive. To reduce
+the number of languages available use the setting ``DOCUMENTS_LANGUAGE_CODES``,
+and set it to a nested list of abbreviations. This setting can be found in the
+:menuselection:`System --> Setup --> Settings --> Common` menu.
+
+For example, to reduce the list to just English and Spanish use
+::
+
+    DOCUMENTS_LANGUAGE_CODES = ('eng', 'spa')
+
+
+The default language to appear on the dropdown can also be configured using::
+
+    DOCUMENTS_LANGUAGE = 'spa'
+
+Use the correct ISO 639-3 language abbreviation (https://en.wikipedia.org/wiki/ISO_639)
+as this code is used in several subsystems in Mayan EDMS such as the OCR app
+to determine how to interpret the document.
+
+If using the Docker image, these settings can also be passed to the container
+as environment variables by prepending the ``MAYAN_`` suffix.
+
+Example::
+
+  -e MAYAN_DOCUMENTS_LANGUAGE_CODES='["eng", "spa"]'
+
+For more information check out the
+:ref:`environment variables <environment_variables>` chapter of the
+:doc:`../parts/settings` topic.
+
+