Adding sessions folder to chmod command for sf3

[elpiel]

I had problem with session cache folder, so I added to the chmod command.
Also the doctrine:fixtures:load command is only available when you've installed the bundle

[leroy0211]

The issue can actually be fixed on another level.
It's because the logs folder (and cache folder) are being created with your host user.
When the containers start, nginx and php are running at a different user and group, which do not have access to the folder.

This could be fixed by having nginx and/or php running on a different user and/or group.
Not sure which one, but I have seen that the nobody:nobody combination is often used.