Restructure documentation

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

docs/chapters/versioning.txt

@@ -0,0 +1,48 @@
+===================
+Document versioning
+===================
+
+Mayan EDMS has the ability to store different versions of the same
+document. A comment field is provided to allow users to summarize the new
+version changes in comparison with the previous one. If a new version was
+uploaded by mistake or such new version is no longer necessary the option to
+revert to a previous version of the document is provided.
+
+.. blockdiag::
+
+   blockdiag {
+      default_shape = roundedbox
+      orientation = portrait
+        node_width = 200;
+      version_1 [ label = "Version 1" ];
+      version_2 [ label = "Version 2" ];
+      document_1 [ label = "payroll_report.pdf" ];
+      document_2 [ label = "payroll_report_fixed.pdf" ];
+      upload_1 [ label = "payroll_report.pdf" ];
+      upload_2 [ label = "payroll_report_fixed.pdf" ];
+
+        upload_1 -> version_1 -> document_1;
+        upload_2 -> version_2 -> document_2;
+        document_1 -> document_2;
+   }
+
+Only the interactive document sources (:doc:`../chapters/sources`)
+(``Web`` and ``Staging folders``) are available to upload new document versions.
+
+There is no limit to the number of versions a document can have.
+
+.. blockdiag::
+
+    blockdiag {
+        default_shape = roundedbox
+        orientation = portrait
+        node_width = 200;
+
+        document [ label = "payroll_report.pdf" ];
+        versions [ label = "Versions", stacked ];
+
+        document -> versions;
+   }
+
+By default, the last version will be showed when working with the document
+but any of the versions can be inspected and viewed.