Files rights in directory tree

Hi,

On Linux systems, care must be given to file rights and modes.

Currently, I try to run Projector'ria in a relatively secure way, so I didn't give write rights to the web server. I've found some improvements to do.

- in zip archive: readme.txt and license.txt are unzipped in the current directory instead of projectorria directory: I've never read them because I havn't got the right to write directly in this directory.
- in config directory: I've found that Projector'ria may rewrite my config file in some cases (upgrades): projectorria/files/config/parameters.php. It's _very_ dangerous and I prefer give specific access if needed.
- I've found that in some cases (updates), files are written in the projectorria/files/cron/ directory. I find it curious because those files vanish away, seemingly...

It'll be cool to dig a bit on security masks to apply to enhance security a bit.

Keep up the work, it's great!