cluster: Removed cluster

Global:
 Removed cluster module import from global scope.

setup:
 cluster: Removed
 end: Removed
options: Default flag to disable rDNS queries
validate

Methods:
 validate: Added the following object to handle validation of
           hostnames (RFC-1123), IPv4, IPv4 CIDR notation,
           IPv4 range notation as welll as IPv6, IPv6 CIDR
           notation & IPv6 range notation.