netbootInstall: RHEL/CentOS updates

Used yum to install the EPEL repo, netatalk to prevent it complaining
about packages installed outside of yum.
Tidied up the tftp config command.
Tidied up the Directory creation.
The netatalk files previously copied were old/had no effect, updated to
edit the in-place files directly.
Created an include for the NetBoot www share, to skip the need to edit
the default httpd.conf.
Added Descriptive names to the user accounts.
Only create the afpuser home if it doesn’t exist (the user add command
handles this in RHEL/CentOS).
Created an include for the SMB share, rather than editing the in-place
config. This will enable the ability to easily enable/disable the share
in the future.
Cleaned up the set permissions commands.