read ocsigen.org-data

1. readdir `DATA_DIR` (ocsigen.org-data) to list and setup projects (lwt, eliom, ..)
2. readdir each project to list versions and configurations
  * every version defines api and manual (no more branches)
  * there is one special version : "dev"
  * some configuration can be found in `ocsigen.org-data/PROJECT/config.js` (json)
    - manual_template, manual_main
    - wiki_id, wiki_id_404, wiki_id_403
  * one can override config for some version pattern (see https://github.com/ocsigen/ocsigen.org-data/blob/master/ocsigenserver/config.js)
  
3. on can add new version (new subdirectory in project directory) and send `ocsigen.org:read versions` to the command_pipe to reload versions  (step 2)

we need to fill missing manuals in `ocsigen.org-data` 
```
Loading versions for eliom
Missing documentation for eliom/1.1.0 api:true manual:false
Missing documentation for eliom/1.2.2 api:true manual:false
Missing documentation for eliom/1.3.4 api:true manual:false
Missing documentation for eliom/2.0 api:true manual:false
Missing documentation for eliom/2.0.1 api:true manual:false
Missing documentation for eliom/2.0.2 api:true manual:false
Missing documentation for eliom/2.1.1 api:true manual:false
Missing documentation for eliom/2.2.2 api:true manual:false
Missing documentation for eliom/3.0 api:true manual:false
Missing documentation for eliom/4.0 api:true manual:false

Loading versions for eliom-base-app

Loading versions for eliom-widgets

Loading versions for goji

Loading versions for js_of_ocaml

Loading versions for lwt
Missing documentation for lwt/1.0.0 api:true manual:false
Missing documentation for lwt/1.1.0 api:true manual:false
Missing documentation for lwt/2.0.0 api:true manual:false
Missing documentation for lwt/2.1.0 api:true manual:false
Missing documentation for lwt/2.1.1 api:true manual:false
Missing documentation for lwt/2.2.0 api:true manual:false
Missing documentation for lwt/2.2.1 api:true manual:false
Missing documentation for lwt/2.3.0 api:true manual:false
Missing documentation for lwt/2.3.1 api:true manual:false
Missing documentation for lwt/2.3.2 api:true manual:false
Missing documentation for lwt/2.4.0 api:true manual:false
Missing documentation for lwt/2.4.1 api:true manual:false
Missing documentation for lwt/2.4.2 api:true manual:false
Missing documentation for lwt/2.4.3 api:true manual:false

Loading versions for macaque

Loading versions for obrowser
Missing documentation for obrowser/dev api:true manual:false

Loading versions for oclosure

Loading versions for ocsigenserver
Missing documentation for ocsigenserver/1.1.0 api:true manual:false
Missing documentation for ocsigenserver/1.2.2 api:true manual:false
Missing documentation for ocsigenserver/1.3.4 api:true manual:false
Missing documentation for ocsigenserver/2.1 api:true manual:false
Missing documentation for ocsigenserver/2.2 api:true manual:false
Missing documentation for ocsigenserver/2.3 api:true manual:false

Loading versions for ocsimore

Loading versions for ojquery
Missing documentation for ojquery/dev api:true manual:false

Loading versions for ojwidgets

Loading versions for tuto
Missing documentation for tuto/2.0 api:false manual:true
Missing documentation for tuto/2.2 api:false manual:true
Missing documentation for tuto/3.0 api:false manual:true
Missing documentation for tuto/4.0 api:false manual:true
Missing documentation for tuto/dev api:false manual:true

Loading versions for tyxml
Missing documentation for tyxml/2.0 api:true manual:false
Missing documentation for tyxml/2.0.1 api:true manual:false
Missing documentation for tyxml/2.0.2 api:true manual:false
Missing documentation for tyxml/2.1 api:true manual:false
Missing documentation for tyxml/2.2 api:true manual:false
Missing documentation for tyxml/3.0 api:true manual:false
```