Added hostname validation features

Added validation of hostname through the addition of a check function,
validate_hostname() and an if statement checking for the return value of
aforementioned function. If the hostname is valid, then the user
supplied value is assigned to the variable. Otherwise, script will
abort. This is necessary to filter out bad values that would otherwise
cause errors that would be mostly invisible to the user without further
investigation.
Added a .com to the default hostname

Adding a .com should prevent errors with the install.sh script.
Added missing argument to validate_hostname

Fixed an issue where validate_hostname was missing an argument
representing the value it was supposed to validate.
Moved validate_hostname check to server name entry

Validation of hostname has been moved from the LDAP hostname to the main
server hostname entry, as this is where it is really needed.
Removed .com extension

Reverted a change where a .com was added.
Merge pull request #66 from ausaccessfed/feature/hostname-validation

Added server hostname validation to check for localhost.localdomain