Add Link structure page to the documentation

doc/md/Link-structure.md

@@ -0,0 +1,18 @@
+## Link structure
+
+Every link available through the `LinkDB` object is represented as an array 
+containing the following fields:
+
+  * `id` (integer): Unique identifier.
+  * `title` (string): Title of the link.
+  * `url` (string): URL of the link. Used for displayable links (without redirector, url encoding, etc.).  
+           Can be absolute or relative for Notes.
+  * `real_url` (string): Real destination URL, can be redirected, encoded, etc.
+  * `shorturl` (string): Permalink small hash.
+  * `description` (string): Link text description.
+  * `private` (boolean): whether the link is private or not.
+  * `tags` (string): all link tags separated by a single space
+  * `thumbnail` (string|boolean): relative path of the thumbnail cache file, or false if there isn't any.
+  * `created` (DateTime): link creation date time.
+  * `updated` (DateTime): last modification date time.
+  

mkdocs.yml

@@ -35,6 +35,7 @@ pages:
     - Continuous integration tools: Continuous-integration-tools.md
     - GnuPG signature: GnuPG-signature.md
     - Directory structure: Directory-structure.md
+    - Link Structure: Link-structure.md
     - 3rd party libraries: 3rd-party-libraries.md
     - Plugin System: Plugin-System.md
     - Release Shaarli: Release-Shaarli.md