[Documentation] Prepare Papyrus-Web to its first deployment

The purpose of this issue is to prepare Papyrus-Web to aa first real deployment.

So we propose to create a new documentation page for the user. This page should introduce briefly Papyrus-Web : What is it ? Who ? Why ? How to start ?

• presentation of the HomePage
• Create a new project
• link to import/export model web <-> locally
• Profile creation/application
• Library usage ?
• How to deploy locally ?
• Licence ? add it on the footer of homepage

Warning: we should avoid to repeat this already available in the userdoc

We should study the possibility to embed this short presentation in the Papyrus website, in order to have a short documentation about the Papyrus-Web capabilites always available, even if the Papyrus-Web instance is down.