Implement access token to ease computer creation.

Allow to query the web site without copy/pasting the user SSL certificates.
The query should be like:
curl -X POST -H "X-Access-Token: ACCESSTOKENVALUE" -d "title=COMPUTERTITLE" "https://slaposmaster.example.org/add-a-server/WebSection_registerNewComputer"

Access token is destroyed after usage.
The token validity is one day.