Added additional parameters to gmetad

I have the need to change the user that gmetad runs as under CentOS 6.x, so I exposed all the params for gmetad. This could probably be cleaned up so gmetad has its own params file (so we can drop the gmetad_ prefix on variables), but this works so far. I also haven't validated gmetad_case_sensitive_hostnames as I'm not entirely sure how I should do this (as it needs to be an integer).