Create zfsinstall-adddisk-geli-beta

This script helps user add a mirror disk to a root pool that was installed with zfsinstall-geli-1disk-beta

Issues:
- must edit the script to match the settings used during zfsinstall-geli-1disk-beta
- do not shuffle the physical disks, must keep the disk in same boot order (ada0 ada1)
- requires geom_nop.ko, zlib.ko, crypto.ko, geom_eli.ko

Passwordless GELI (unsecure):
- add "-P" right after "geli init"
- add "-p" right after "geli attach"