Replacing ${_wSlice} by ${_pSlice} for GPT.

GPT can not be us like MBR. We can not create label in the GPT partition like MBR.
Adding the GhostBSD GPT option.
Adding the GhostBSD way for gpt partitioning.
Adding missing fi
Adding gpt partitioning the GhostBSD way.
removing -a on [ "${INSTALLTYPE}" = "GhostBSD" ]
removing -a on [ "${INSTALLTYPE}" = "GhostBSD" ]
Update functions-users.sh
Merge pull request #15 from ericbsd/master

Adding GPT partitioning for GhostBSD and deleting live user. -

I will be taking a look at the "gptslice" stuff in the future. I may need to revert those changes, since it was a special disk-setup for "BootCamp" on macs, not sure if it works differently on FreeBSD > 10.x.