Adding Swap to Vaprobash

- See #338
- Adds optional Swap to the Vagrant box using a new variable called `server_swap`. Set it to `false` if you don't want any Swap.
- Will fix #336
Some minor "improvements" based on laravel/settler

- Added redis_persistent variable
- Using PPA:rwky/redis for latest stable redis
- Added php5-redis
- User "vagrant" is added to "www-data" group in base.sh
- PHP5-fpm, Nginx and Apache now run as the "vagrant" user and "vagrant" group
- Added some more PHP config (memory_limt is set to 256MB instead of 128MB, cgi.fix_pathinfo is disabled, ...)
- Cleaned up "Enable remote acces" in mysql.sh and maria.db
- The variable booleans check are case-insensitive and space-insensitive (ie "true", "True  ", "TRUE" are all recognized as true).