Add Installation pages documentation

* Close #1
* Add installation page about all OS
Don't forget images data

* Close #2
Correct wp-content old ressources

* Move picture to images directory
Add links page

* Some external ressource about gephi and its univers
Legal pages

* Restor legal page as copyright, licence,  privacy
Marketing page

* spread-users added and by requirement marketing page
* Some pictures added and set in specific directory images/badge
Add support page

* And missing page linked
Some other legals page

* Some other legal page are linked from at least toolkit page
Toolkit page

* Some picture and correct links from toolkit page
Developer introduction page

* Better to provide also an introduction developper informations