Application authentification

**Store a token for each application in tokenFile.**
Token file has a 700 permission for cozy-<app.user>.
Token is changed each start of application.
Applications home, proxy, data-system and controller share a similar token.

**Directories which contain pid files and token files can be configured :**
Configure tokens directory : 

    cozy-controller --tokensDir '/etc/tokens'
    '/etc/cozy/tokens' by default

Configure pids directory : 

    cozy-controller --pidsDir '/etc/pids' to change pids directory
    '/etc/cozy/pids' by default