update configuration in vagrant-lemp

- added directory 'contrib/vagrant/src/' which will be mounted by
  Vagrant in '/srv/www/sites/default/' on the web host. Directory
  'public/' is a root of the webserver and should be ignored by git;

- fixed PHP5 group of the web host, PHP5 should now be correctly
  installed and configured;

- main ginas project directory will be mounted in '/home/vagrant/ginas/'
on 'master' host for easy access and Vagrant bootstrapping;