Restructure documentation

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

docs/chapters/file_storage.txt

@@ -0,0 +1,36 @@
+============
+File storage
+============
+
+The files are stored and placed under Mayan EDMS "control" to avoid
+filename clashes each file gets renamed to its ``UUID`` (Universally Unique ID),
+without extension, and stored in a simple flat arrangement in a directory.
+
+.. blockdiag::
+
+   blockdiag {
+      default_shape = roundedbox
+      file [ label = 'mayan_1-1.pdf', width=120];
+      document [ label = 'mayan/media/document_storage/ab6c1cfe-8a8f-4a30-96c9-f54f606b9248', width=450];
+      file -> document [label = "upload"];
+
+      file -> document;
+   }
+
+This doesn't stop access to the files but renaming, moving or updating
+directly them is not recommended because it would throw the database out
+of sync.
+
+Because Mayan EDMS components are as decoupled from each other as possible,
+storage in this case is decoupled and its behavior is controlled
+not by the project but by the ``Storage`` module class. All the other
+modules don't make any assumptions about how the actual document files are
+stored. This way files can be saved locally, over the network or even across
+the Internet and everything will still operate exactly the same.
+
+The default file storage backend: ``storage.backends.filebasedstorage.FileBasedStorage``
+is a simple backend that only supports paths and not IP addresses. In case you
+are interested in using remote volumes to store documents (NFS, SAMBA), first
+mount these volumes so that they appear as a directories to Mayan EDMS. For
+direct support for remote volumes a custom backend would be needed such as those
+provided by the Django Storages project (https://django-storages.readthedocs.org/en/latest/).