Ds 1660 hiera fixup

Defined a new level in the hiera.yaml file, called "local" which allows you to override settings in common.yaml by creating a local.yaml file. Added all .yaml files (other than common.yaml) in the config folder to a new .gitignore, so local configs won't get committed accidentally. Also removed the hard-coding of options in the dspace-init.pp Puppet manifest file, as these parameters will override the settings coming from hiera.